bluuebunny/crossref_metadata_2025 huggingface dataset:
Parallel Computing of Laser Propulsion with Hypergraph Partitioning
Authors: Zeng Yao Yuan , Zhao Wen Tao , Wang Zheng Hua
Published: September 2013

As one of the most important methods to study laser propelled rocket, the numerical simulation of laser propulsion has drawn an ever increasing attention at present. Nevertheless, the traditional serial computing cannot satisfy the practical requirements because of high calculation precision, insatiable memory overhead and considerable computation time. In this paper, we study on a general algorithm for laser propulsion, and divide the computing domain by using a multilevel hypergraph partitioning algorithm. Furthermore, MPI allreduce, overlapping communication with computation and non blocking communication are adopted to decrease the communication time when dealing with global communication. Finally, parallel performance about two typical configurations on a China-made supercomputer shows the smallest value of speedup ratio is more than 123 when the number of processors is 256. In conclusion, our parallel method is effective and practical in numerical simulation of laser propulsion.
The Design and Implementation of Reconfigurable Cipher Unit on FPGA
Authors: Zhang Wei Ping
Published: September 2013

Encryption is the core of security technology. The paper managed to design and implement a kind of reconfigurable cipher unit based on the 3DES/AES and optimized by FPGA technology, which can effectively support diverse cryptographic algorithms and can meet the demand on system performance and flexibility. The unit uses hardware description language VHDL, layout and wire on QuartusII8.0. Finally the system is downloaded to DE2 for testing. The design hardware structure is simple, flexibility, security, which can be widely used in the field of information security.
Analysis of Optimal Spectral Efficiency with Adaptive Modulation Coding and Cooperative ARQ Protocols
Authors: Li Xiu , Huang Sheng Ye , Yan Yuan Yuan , Liu Jia Jie
Published: September 2013

In this paper aiming at maximizing the spectral efficiency, a cross-layer design which combines adaptive modulation and coding (AMC) at the physical layer and truncated automatic repeat request (ARQ) protocol at the data link layer in cooperation system is proposed. In order to analyze the system performance, we first derive a closed form expression of probability density function (PDF) of the received signal-to-noise (SNR) using maximum ratio combing (MRC) at the destination node, the theoretical results and simulation show that the new design outperforms the traditional AMC system especially at low SNR.
Research on the Near-Infrared (NIR) Photon Migration in the Knee
Authors: Chen Yan Ping , Ma Xiong , Li Chun Bin , Chen Song Qing
Published: September 2013

To study the phenomena of photon migration in the knee joint is very important in the field of non-invasive near-infrared optical early diagnosis of osteoarthritis of the knee (KOA). In this paper, a photon propagation model of the knee layered structure based on Monte Carlo method is proposed. The migration trace and distribution rule of the photons in knee layered structure are simulated by the Monte Carlo modeling. The proportion of photons which collide with bone tissue then migrate out of the muscle tissue and photons directly migrate out of muscle tissue is calculated and analyzed. The conclusion is that the MC method provided in this study is useful to analyze the photon migration in knee layered structure and to place the detector in a suitable position.
A New Two-Sided Coupling Channel Drop Filter Based on a Two-Dimensional Photonic Crystal
Authors: Zhang Xiang Nan , Liu Gui Qiang , Hu Ying , Cai Zheng Jie , Chen Yuan Hao
Published: September 2013

We design a new two-sided coupling channel drop filter (CDF) based on a two-dimensional (2D) photonic crystal (PC). Three channels formed by line defects for light propagation, two L4 resonators positioned at both sides of the input waveguide for light coupling, and one point defect micro-cavity in the bus waveguide for wavelength-selective reflection are introduced into the PC structure. The optical characteristics of this proposed structure are calculated by finite-difference time-domain (FDTD) method combined with the perfectly matched layers (PMLs) as the boundary conditions. Three wavelengths centered at 1550, 1575 and 1610 nm within the limit of communication windows are successfully separated in three channels by adjusting the size of coupling rods and the positions of L4 resonators and micro-cavity. High transmission efficiency and more than 20 nm channel spacing are achieved. These demonstrate that our proposed structure is suitable for photonic integrated circuits (PICs) and coarse wavelength division multiplexing (WDM) optical communication systems.
A Novel Integrated MEMS Pyramidal Horn Antenna for Terahertz Applications
Authors: Guo Lin , Huang Feng Yi , Tang Xu Sheng
Published: September 2013

This paper reports the design and analysis of a novel pyramidal horn antenna based on Micro­electromechanical Systems (MEMS) technology, which is used in terahertz (THz) applications. The structure of the antenna includes two parts, pyramidal horn and inverted pyramidal horn for feed, the fabrication of the structure needs only one wafer, and the antenna can be easily integrated with other parts of on-chip circuits. There are many tunable parameters of the horn, so that high performance THz antenna can be achieved by optimizing these parameters. The proposed antenna can be manufactured by MEMS processing with low fabrication cost, suitable for many terahertz systems.
Research of LED Lamp Constant Current Driver Software System
Authors: Liu Ling
Published: September 2013

The LED lamps replace traditional lamps is the direction of development domestic and abroad.It mainly introduced the LED lamp brightness control method from the aspect of software, then research and production of the LED efficient drive based on a IC chip digital boost constant current regulator, for the actual driving high power LED. It was realized 6 level control on the brightness of LED. The microcontroller controls D/A converter to make the output different voltage values through software programming, and then adjusts the DC/DC conversion circuit current size, finally implements LED brightness control. The experimental makes it possible to have the lamp with adjustable brightness, energy saving, achieve a wide range of voltage, current constant and so on.
Heat Dissipation Simulation Research of LED Downlight and Optimization of Light Source Layout
Authors: Chen Jie , Chen Zhong , Chen Jie , Li Xiao Hong , Shen Ya Feng , Xiong Jing Kang , Wang Yang Xia
Published: September 2013

In order to solve the heat dissipation problem of LED (light-emitting diode) downlight, CFD thermal simulation software was used to establish LED downlight dissipation model. Materials thermal conductivity, thermal resistance, thermal emissive values, heat load forms and other factors were all taken in considered, and then numerical simulation combined with laboratory measurement methods was used to analysis the lamps dissipation. Based on this method, focused on the dissipation effect with different LED quantities and LED ring distances, and then optimized light source layout of current LED downlight products. After experimental verification, LED working temperatures were more ideal after the light source layout optimized, and it can improve the LED lamp lifetime effectively, this result also has important practice significance in the future LED downlight design process.
Modeling and Analysis of Grid-Connected Inverter for PV Generation
Authors: Cao Neng , Cao Ya Jun , Liu Jiao Yu
Published: September 2013

In order to improve the efficiency of photovoltaic generation as well as the power quality, grid-connected inverters for PV generation research was carried out for photovoltaic maximum power point tracking. Based on some current studies on the incremental conductance method, an advanced incremental conductance control algorithm was proposed, which can track maximum power point rapidly and accurately. The oscillation phenomenon, which exists near the maximum power point, was improved at a great extent, so to the efficiency of photovoltaic cells generation electricity. The inverter control system has an advantage in its high speed and flexibility by applying advanced control algorithm. And the source harmonic current is remarkably reduced. In addition, the power factor is enhanced and the power quality is improved. Finally, according to the principle of inverter control system and based on the analysis on the mathematical model of photovoltaic inverter, a simulation model of that is established based on MATLAB/SIMULINK.
Carrier-Phase Differential GPS/INS Integrated Navigation System
Authors: Zhang Lu , Yang Gong Liu
Published: September 2013

According to high accuracy demand in the measurement field, this paper designs a high precision inertial measurement system by using DSP and ARM processor to realize carrier-phase differential GPS/INS integrated navigation. This paper chooses Kalman filter to estimate the systematic error, uses closed loop method to correct, and carries out carrier-phase differential GPS/INS data fusion. Through manipulating actual measurement data, the integrated navigation results indicate that position accuracy reaches cm level; velocity accuracy reaches cm/s level and attitude achieves high precision. The experiment proves the feasibility and effectiveness of carrier-phase differential GPS/INS integrated navigation system.
New FSE Based on MCMA and PLL
Authors: Liu Yan , Li Yuan Min
Published: September 2013

In the digital transmission system, an efficient fractionally-spaced equalizer (FSE) for blind equalization based on modified constant modulus algorithm (MCMA) and phase locked loop (PLL) is proposed. Comparing with conventional FSE based on famous CMA, the proposed algorithm has not only lower steady-state mean square error and faster convergence rate but also the ability to recover carrier phase rotation. The efficiency of the method is proved by computer simulation.
Bit and Power Allocation Algorithm for OFDM UWB Systems
Authors: Li Hai Yan
Published: September 2013

Ultra-wide-band (UWB) is a promising short-range indoor wireless communication technology for large communication capacity, high transmission rate, low power consumption, etc. Multi-band orthogonal frequency-division multiplexing ultra-wide-band (MB-OFDM UWB) system can achieve much higher anti-noise capability and flexibility. However, the transmission power of UWB systems is strictly restricted for avoiding the interference with other wireless communication systems existing in the same frequency spectrum range. It is necessary that adequately utilizes channel estimation to allocate bit and power effectively. According to the change of channel gain, UWB systems modify the allocation factor to optimize the performance of systems and reduce power allocation remainder. Simulation shows modified bit-power allocation algorithm can enhance power allocation efficiency. Furthermore, it is found that the power remainder of modified allocation factor algorithm is less influenced by the bit error rate.
Analysis and Design of E-Shaped Dual-Frequency Microstrip Antenna Based on CPSO Algorithm
Authors: Ao Wei , Xiang Wan Qin , Chen Chun Ming , Tian Wei , Zhang De Bin
Published: September 2013

In order to solve the problem of design and optimization for E-shaped patch microstrip antenna, chaotic particle swarm optimization (CPSO) algorithm was proposed to assist the procedure. First, the E-shaped antennas model was created, and then, the parameters of this antenna were adjusted according to the CPSO algorithm, and the procedure was repeated until the antennas capabilities meet the requirements. The simulation results showed that, the optimized model of such antenna, was capable of dual-frequency operation in 1.8GHz and 2.4GHz, and it was also capable of wide bandwidth, could meet the requirements very well.
The Fiber Grating Signal Acquisition System Design Based on FPGA and USB Interface
Authors: Zhao Yi Zhu , Wan Sheng Peng , Peng Di , Liu Dong Dong
Published: September 2013

Design a high-precision real-time high-speed sampling fiber grating demodulation signal system based on a USB2.0 interface and FPGA; system hardware design and software design are introduced in detail. It is proved that has a good reliability and stability by the experiment. So this design has a strong value in use.
A Fiber-Gating Intelligent Adaptive Alarm Algorithm Based on Wavelet Analysis
Authors: Wang Zhi Ming , Zhang Xia
Published: September 2013

For Fiber-Grating Perimeter-Intrusion alarm system, a Fiber-Grating intelligent adaptive alarm algorithm based on wavelet analysis and difference algorithm was proposed. The algorithm precedes the real-time waveform by wavelets decomposition, and acquired the assertion values of each subband by difference calculation. Through the method of comparing the assertion value of some subband, intelligent adaptive alarm system was realized. The experiments indicate that the proposed algorithm can give an alarm for illegal intrusion with good performance and false alarm below 1.5%, and it provides a promising application prospect for intelligent adaptive alarm.
Aware Handoff Algorithm Based on the Location of the 3G and WIFI
Authors: Liu Yang Hong , Yang Xiao Hui
Published: September 2013

This paper analyzes the shortcomings of traditional handover algorithm, based on location aware switching the algorithm joined the GPS geolocation information to get the precise location and movement information to avoid unnecessary delay in the detection, switching between 3G and WIFI. The simulation results show that the performance of the algorithm with respect to traditional purely based on the received power switching algorithm significantly improve.
A Method for Real-Time Radar Signal Main Sorting
Authors: Wu Hong Chao , Xiao Wei Hua , Pu Jian Feng
Published: September 2013

The real-time radar signal sorting is one of the key technologies for electronic reconnaissance, first analyzes the defects of traditional main sorting algorithms, and then proposes a comprehensive main sorting algorithm. The method first uses the SDIF algorithm to sort PRI fixed and PRI stagger radar signal, then uses dynamic expansion association method to search PRI jitter radar signal. When using the SDIF algorithm, in order to improve the efficiency of extraction of PRI, first taking amplitude pretreatment, then only accumulate the signals whose amplitude meet certain requirements. After extracting PRI, extract to the original full pulse sequence. Simulation results show that the method of sorting has high accuracy and good real-time.
Photosensitivity Improvement in Multi-Component Doped Photopolymer
Authors: Geng Yao Hui , Yu Dan , Liu Hong Peng , Lv Jiang
Published: September 2013

Multi-component doped photopolymer with phenanthrenequinone photosensitizers is prepared and its photosensivity characteristic is investigated experimentally. SiO2 nanoparticles and ZnMA organometallic components are dispersed into the P(MMA-co-MAA) matrix to enhance the photosensitivity of sample. Experimental results indicate the photopolymerization time constants under consecutive exposure and the time constants of dark enhancement under darkness are evidently reduced at least one order of magnitude.
White Electroluminescence Using Eu-Complexed Copolymer as the Red Unit
Authors: Zhang Wen Guan , Qin Lian , Zhao Sheng Min
Published: September 2013

Europium complexes exhibited intense red fluorescence with a narrow spectral bandwidth. But non-uniform blending or dispersion of complex resulted in phase separation, decomposition and inefficient energy transfer to reduce emission efficiency. The complexes were covalently attached to the main chain of polymers, which improved film quality and solubility. Eu (TTA)2(AA)(TPPO)2 as europium complex monomer (ECM) was prepared by Eu3+ coordinating with triphenylphosphine oxide (TPPO), acrylic acid (AA) and 2-thenoyltrifluoroacetone (TTA). Fluorescent Polymer marked as p1-30 (molar ratio for ECM/N-vinylcarbazole (NVK), 1/30) was synthesized. The emissions of ECM and p1-30 peaked at ca. 610 nm. The highest occupied molecular orbit (HOMO) and the lowest unoccupied molecular orbit (LUMO) energy levels were-5.36 and-1.99 eV. The organic light-emitting devices (OLED) A ITO/PEDOT: PSS/PBD: p1-30/AlQ3/ LiF/Al and B ITO/PEDOT: PSS/PBD: p1-30/BCP/AlQ3/LiF/Al were fabricated. A 4 nm thickness of BCP as a hole-block layer was introduced in Device B to block the movement of holes partly and to reduce the emission from AlQ3. Devices A and B mainly emitted white emission and exhibited luminance of 420 and 315 cd/m2 with Commission International de LEclairage (CIE) coordinates of (0.317, 0.392) and (0.336, 0.380), respectively. The emission from carbazole moieties was suppressed, electroluminescent (EL) spectra revealed that effective intramolecular energy transfer from carbazole unit to europium complex occurred.
Fourth-Harmonic Generation of High-Repetition Femtoscond Ti:Sapphire Laser by a BBO Crystal
Authors: Li Ma Guo , Hui Yi Hou , Dong Chen Qing , Jun Ji Yan , Wei Han Jing
Published: September 2013

Fourth-harmonic generation of an 82MHz femtosecond Ti:sapphire laser oscillator has been demonstrated by the sequential sum-frequency mixing design with BBO crystals. Frequency quadrupling of a mode-locked Ti:sapphire laser results in maximum average power of 7mW at 82 MHz with the pulse duration of 200fs. The shortest wavelength achieved is 196.5 nm.
Experimental Study of Low-Pressure Water Jet Assisted Laser Drilling on Al2O3 Ceramic
Authors: Pang Zhi Wei , Yuan Gen Fu
Published: September 2013

A study on low pressure water jet assisted laser processing is presented. This new method is researched by drilling on Al2O3 ceramics material. A comprehensive research on the influence of laser processing parameters on surface quality with this method is conducted. The microcosmic appearances of the machining surfaces obtained from normal laser processing and composite processing were comparatively analyzed. At the same time, through measuring the holes in the 3-D morphology, the influences of water jet velocity and laser processing parameters on the surface quality are presented. The results show that, the surface quality is significantly improved with this new method which combines low pressure jet into laser processing. The molten slag can be significantly reduced and the stability of processing quality can be improved much.
Synthesis of Graphene Load Nickel Nanoparticles Composites with Hydrothermal Process
Authors: Fu Yue , Cui Wen Jing , Yan Fei , Zhao Dong Yu
Published: September 2013

This paper presents a synthetic method of graphene load nickel nanoparticles composites. Hydrothermal process is simple and convenient way, neither surfactant is needed nor by products will exist serve hydrazine hydrate as reductant. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) analyses were used to characterization the morphology of the graphene load nickel nanoparticles composites, and cyclic voltammetry (CV) was used to characterization the electrical properties of the composites. The results of XRD and FTIR show that the complexes were successfully synthesized by this method. Moreover, the good dispersibility and relatively uniform particle size of the complexes can be obviously observed from the SEM image. And the cyclic voltammetry curves exhibit good electrical properties of graphene load nickel nanoparticles composites. All the conclusions are based on the experimental results.
Effect of Sintering Time and Heating Rate on the Structure of LiFePO4/C Prepared by Electrospinning
Authors: Zhang Chang Huan , Liang Yin Zheng , Qiu Yi Ping
Published: September 2013

The electrospinning combined with the sintering process were used to prepare carbon-coated lithium iron phosphates (LiFePO4/C) cathode materials for lithium ion batteries (LIB). In sintering process, different procedures were used to synthesize the LiFePO4/C composite materials. The effect of the sintering time and heating rate on the structure, surface morphology and carbon content of LiFePO4/C composite materials were investigated by wide angel X-ray diffraction (WXRD), scanning electron microscope (SEM), and elemental analysis (EA) techniques. It has better structure when the sintering process is as follows: heating rate is 2 oC min-1 and pre-oxidized time is 3h at 280 oC and carbonized time is 8h at 700 oC.
Petri Based Formal Verification of Data Session Transmission for Lighting Control System
Authors: Jiang Yu Jian , Jiang Wei , Ren Hui
Published: September 2013

In this paper, traditional data transmission strategy of lighting control system is compared. Defects are analyzed. Through Petri based formal verification, the Petri model of SDT is built. Rationality of the model and SDT is validated, which proves that SDT is reachable. Reliability and circulation characteristics of the protocol are also proved.
Design and Analysis of a New Dynamic Tracking Performance Testing System
Authors: Tan Bi Tao , Guan Xiao Wei , Chen Li Zi
Published: September 2013

Rotating target is the main equipment used to test tracking performance of electro-optics system indoor, but it can only simulate a single track, so a new dynamic tracking performance testing system is designed, which can offset the disadvantage of the rotating target. In this paper, the new testing systems basis structure is given, then the movement track theory model of the system is established, and the space relation between the testing system and the electro-optics system is deduced. At last, the movement track, tracking velocity and tracking acceleration is simulated through computer, the simulation results proved that the new testing system can simulate more movement track, make the multi-tracking velocity and multi-tracking acceleration realization, and can test electro-optics system more comprehensive.
Semantic Similarity Measure Based on Concreteness Degree of a Concept
Authors: Li Wen Qing , Sun Jia Feng , Lu Wen Qin , Zhang Yong Le , Zhao Pu
Published: September 2013

Semantic similarity between concepts is widely used, but the measuring method is still a challenging task. We proposed a semantic similarity measuring method, using concreteness degree of a concept which is based on constructing process of ontology. Firstly, Concreteness degree of concept was defined for the concept by depth of the concept itself and its most specific descendant, then according to the Jaccards Coefficient the semantic similarity between concepts measured by the specified process of the two compared concepts and their co-specified process. Experiment result shows that the proposed method gained a higher correlation coefficient to human judgments than other compared measures.
Test Methods Research and Verify for FPGA
Authors: Shu Ji Shi , Liu Yuan Sheng
Published: September 2013

This paper mainly introduces the principle and usage of dynamic probe technology, and makes comparisons between traditional test method and the most popular debugging methodutilizes the embedded tool of debugging on chip to debug. The research depends on self-designed FPGA test service system based on dynamic probe technology. It also explores how to use existent tools and technology for high efficiency test method in FPGA debug and verify process. Through comparisons, it is possible conclude that dynamic probe technology is able to cope with the complex test requirements, and provide more accurate sampling data than the general method in the debugging process. More importantly, the dynamic probe can complete switching a group of the internal signal to be measured within a few seconds, which greatly reducing the waiting time of debugging.
Research and Realization on IVI Driver
Authors: Li Zhi , Zhang Huo , Zhu Wang Chun
Published: September 2013

As an important part of LXI instruments, IVI driver provides instruments a unified programming interface. It brings convenience to the development and maintenance of automatic test system, and meets the requirements of LXI bus for instrument interchangeability. IVI driver architecture and implementations based on IVICOM are analyzed. An IVI-COM driver of a LXI instrument is designed and implemented, and a test program for this IVI-COM is built. Test result shows the right functions and interchangeability of the designed IVI COM driver.
The Vibration Modal Testing and Analysis of an Experiment Gun Mount
Authors: He Lei , Zhang Jian , Zhou Ke Dong , Gong Peng Han
Published: September 2013

An experiment gun mount system is used to clamp the small arms and replace gunner to conduct the automatic shooting in the shooting accuracy test. Because of the concomitant phenomena such as high shock and vibration when shooting, to study the vibration characteristics of the system, a modal analysis method was proposed and the experimental points, including the exciting points and the vibration pickup points, were determined on the basis of its geometric model. Based on the Fast Fourier Transform technique, the CRAS modal testing system was built. The modal experiment of the system was carried out by hammer blow method. The exciting signals, spectra of impacting prompt power, vibration acceleration and their frequency response functions were obtained. The first six order vibration modes, damping ratio and the corresponding vibration frequencies were obtained, which laid the foundation for dynamic response calculation and further optimization design of the system in the future.
Design and Implementation of Teaching Affairs Management System Based on .NET in Colleges and Universities
Authors: Du Dong Ju , Shao Hai Long
Published: September 2013

The mixed mode of C/S and B/S and .Net Technology are applied to presenting the design and implementation methods for .NET-based information system of teaching affairs management in colleges and universities through deeply analyzing teaching affairs management system in colleges and universities as well as combining with system characteristics.
A Multi-Agent Management System for Grid Resource Allocation
Authors: Kang Wang Lin , Liu Xin Min , Wang Kai
Published: September 2013

This paper designs a decentralized resource multi-agent system based on a novel reverse auction protocol. In the implementation of this multi-agent system, first the multi-attribute bids offered by the provider agents are calculated based on the users preference value function. Furthermore, an on-line reverse auction mechanism is provided to describe the on-line situation. I.e., the different grid resource provider agents arrive at different times and this mechanism is required to make an immediate decision about each bid as it is received. Numerous simulating experiments show that the proposed reverse auction method is effective in resource utilization and has better performance in user utility.
Structural Performance Analysis and Repair Design of Wenxing Lounge Bridge
Authors: Chun Qing , Sun Lan Xiang
Published: September 2013

Lounge bridges in Taishun are a special type of Chinese traditional timber structure. Wenxing Lounge Bridge is a famous bridge of them. The analysis of structural performance and damages for Wenxing Lounge Bridge is the foundation of its repair and reinforcement. The performance degradation of wood material and the action of strong external force and the effect of environmental changing and the factor of unfavorable human-activity have continuously accelerated the damage of the bridge. After visiting local craftsmen, building technics and detailed conformations of the bridge are researched. The FEM analyses on the structure before damaged and after damaged are carried out respectively. Damages reasons of the bridge are then generally analyzed and repair design of the bridge is also presented.
Diagnostic Evaluation of Insect Attack on Existing Timber Structures: A Review of some Case Studies
Authors: Feci Elisabetta , Mannucci Massimo , Palanti Sabrina
Published: September 2013

The problem of wood-boring insect attacks is gaining greater interest in Italy today. Wood-boring insects (Coleoptera, termites) often cause both structural and aesthetic damage on wooden structures which can sometimes give rise to human health concerns. Possible causes of current insect infestations include the use of timber originating from plantations, as well as bad post-felling practices such as late harvesting and stocking in unsuitable places before final processing. In the past, these insects were not thought to pose an economic threat to timber in service in Italy, but, in recent years, they have become a problem. The aim of this paper is to report on case studies concerning the occurrence of these unusual wood-boring insects on timber in service and, on the basis of the Authors experience, to formulate an in situ inspection protocol. The species we are dealing with in the case studies are: Bostrichus capucinus, family Bostrichidae, associated with Lyctus spp. (Fam. Lyctidae) and Lymexylon navale, family Lymexylonidae, belonging to the group of the so-called ambrosia beetles or pinhole borers. All these species were found on hardwoods, where they had bored into the sapwood except for L. navale which was also able to bore into heartwood, causing major concerns about its potential danger to timber in service. A technical integrated approach in evaluating insect attacks on on-site timber elements is also described here. The assessment is based on different methods, i.e. visual inspection and acoustic detection. This procedure is proposed as a basis for the development of an intervention protocol in the early stages of infestation.
Antique Wooden Floor Construction Solutions and the Possibilities of Using them in Reconstructions
Authors: Rozanska Anna , Sudol Ewa , Wierzbicki Jaroslaw , Mazurek Andrzej
Published: September 2013

The article describes diverse solutions used in the construction of antique wooden beam-structure floors and analyses the viability of their application in reconstructions. The function of the individual layers of their structure is analysed by: 1.Comparing elasticity (shock absorption in accordance to the PN EN 14808:2005 standard) of floors with continuous support (joists lying on a mineral base and joists placed on a layer of sand) with parquets that have punctual support. 2.Comparing the elasticity of parquets lying on a boarding and those placed directly on joists. 3.Analysing the function of woodwork parquet joints in the floor structure. The capability of floors from antique manor houses in South-Eastern Poland to transfer own and usage loads is being assessed in order to make recommendations as to their preservation, relocation or substitution.
Wooden Boards Arches Roofs in Late Nineteenth-Century Industrial Architecture: Conservation Problems
Authors: Mattone Manuela
Published: September 2013

The maintenance and preservation of wooden structures which are a significant part of historical building heritage requires suitable knowledge of both the material on which intervention is intended and the construction techniques used to build it. Understanding its structural design, characteristics, and construction specificities is crucial in order to correctly safeguard this aesthetical/cultural heritage of knowledge and values which in some cases has, unfortunately, been irremediably lost.The present contribution will analyse several examples of wooden structures built using the system invented by Philibert de lOrme in 1561. The case studies, all cited in the Nouvelles Inventions pour bien bâtir à petits frais, illustrate the different ways in which the construction system proposed by de lOrme can be used.
In Situ Assessment Method of Wood Using Normalized Withdrawal Resistances of Metric-Screw Type Probes
Authors: Yamaguchi Nobuyoshi
Published: September 2013

Withdrawal resistances of wood have been applied for in situ assessment of wood in existing timber structures. The author had proposed method to estimate shear strengths of wood from measured withdrawal resistances of probes which are screwed into wood. In order to verify the accuracy of these estimated shear strengths by proposed methods, withdrawal resistance measurements and shear loading tests were conducted for wood. Single withdrawal resistance measurement was applied for wood specimens, and estimated shear strengths from withdrawal measurements were compared to the measured shear strengths by shear loading tests of wood. Correlation between the estimated shear strengths and measured shear strengths of specimens was reasonably good (R2=0.73). Multiple coaxial withdrawal resistance measurement which can provide distribution of shear strengths in cross-section of wood was also proposed. The average of estimated shear strengths by single withdrawal resistances was 7 percent less than that of measured shear strengths. The average of estimated shear strength by multiple coaxial withdrawal resistances was 3 percent greater than that of measured shear strengths. The single withdrawal measurements and multiple coaxial withdrawal resistances are available to estimate shear strengths of wood and shear strength distribution in the cross-section of wood. Estimated shear strengths obtained from these methods will be valuable for strength based in situ assessment of wood.
Application of Non-Destructive Techniques in the Inspection of the Wooden Roof of Historic Buildings: A Case Study
Authors: Morales-Conde M. Jesús , Rodríguez-Liñán Carmen , Rubio de Hita Paloma
Published: September 2013

The aim of this paper is to show the results of applying non-destructive inspection techniques (thermography, ultrasounds and microdrilling) during the inspection works of a protected building. These non-destructive techniques have been applied in the inspection of the wooden roof to identify deterioration, density loss and defects as a means of assessing its conservation status. This work concludes that the union of these nondestructive techniques constitutes an accurate diagnostic tool for the on-site inspection of wooden structures and the evaluation of their conditions. Thermography allows to distinct moisture contents while ultrasound detects density loss in areas of the wood with high moisture content.
Failures of the Listed Wooden Buildings in Istanbul
Authors: Kuruscu Ali Osman , Arun Gorun
Published: September 2013

Istanbul, which has been the capital city of different empires throughout history, houses numerous listed architectural and cultural historical buildings. There are diverse applications of timber structures all through Anatolia. As capital city of Ottoman period, construction of timber had high and low periods in Istanbul. As masonry houses have suffered numerous intense and destructive earthquakes, wooden buildings gained importance to be safe especially among rich people. As several fires wiped out thousands of houses and the districts, masonry buildings were made obligatory by law in the form of building regulations. Later however, due to many damages caused by repeated earthquakes, construction of timber buildings was once again allowed under the law. Between the 15th and the 18th centuries, the Turkish dwellings of timber framed construction with brick filling were developed. After the 18th century, the quality of work was decreased; the wall frames constructed without any filling sheathed with timber planks or lathed plaster became popular.
Today, although these timber dwellings are listed, they are in very poor condition due to lack of maintenance and wrong interventions. In order to make risk assessment of these structures, more than 20 houses were inspected in Historical Peninsula of Istanbul. This paper will discuss risks sources, assessment of damage level and evaluation of the present condition of these buildings.
Development of Radar Apparatus for Scanning of Wooden-Wall to Evaluate Inner Structure and Bio-Degradation Non-Destructively
Authors: Fujii Yoshihisa , Fujiwara Yuko , Yanase Yoshiyuki , Mori Takuro , Yoshimura Tsuyoshi , Nakajima Masao , Tsusumi Hiroki , Mori Mitsunori , Kurisaki Hiroshi
Published: September 2013

A nondestructive and small FMCW radar apparatus for scanning of the wooden wall to evaluate inner structure and biodegradation progressed in the wall was developed, and the performance of the apparatus was investigated. The allocations and the properties of the construction members in the wall, such as wooden posts and beams, metal plate connectors and insulating materials was recognized as 2D and 3D images. The moist area of more than 50% in moisture content in the wall was also recognized, and this suggests that the area of potentiality of biodegradation such as fungal and insect attacks in the wall can be detected by this apparatus. The feasibility of the apparatus to evaluate of the loss in the wood substance caused by the bio-degradation was also confirmed.
Determination of the Stress Distribution in Timber Elements Reinforced with Self-Tapping Screws Using an Optical Metrology System
Authors: Ayoubi Mazen , Trautz Martin
Published: September 2013

The use of self-tapping screws with continuous threads to reinforce and join timbers in addition to glulam elements represents an effective, simple and economic method. The high withdrawal resistance of the screws as well as its continuous bond with the wood enables an effect similar to steel reinforcement in concrete structures.
Within the framework of a research project, funded by the German Research Foundation (DFG) at the Chair of Structures and Structural Design in cooperation with the Institute for Building Material Research of the RWTH Aachen University, several tests have realized to investigate the bond behaviour, the force transfer and the anchorage length of the screws.
Herewith the stress distribution will be determined with an optical 3D field measuring system, based on the digital image correlation (DIC) method, which measures the strain by observing the surface of the test specimens. To ensure the accuracy of the measurements for a wide measuring field of wood surface, a comparison study was conducted involving traditional electrical sensors (i.e. strain gauges and LVDTs). The results of this study, which confirm the accuracy regarding the determination of stress distribution for small deformations on the wood surface with optical 3D field measuring system, will be presented in this article.
Characterization of Wood Fracture Using Optical Full Field Methods
Authors: Pop Octavian , Dubois Frédéric , Méité Mamadou , Absi Joseph
Published: September 2013

In this paper a new formalism based on the complementarity between the optical full field techniques and integral invariant Mtheta is proposed in order to evaluate the fracture parameters in cracked specimen made of wood, under mixed mode loadings. The coupling between the experimental and numerical approaches allows identifying the fracture parameters in terms of energy release rate without any the material elastic properties such as the elastic modulus and the Poissons ratio. The proposed formalism allows also determining, in addition with the fracture parameters, the local elastic properties in terms of reduced elastic compliance. The fracture mixed mode tests are realized using a Single Edge Notch sample made in Douglas with the Arcan fixtures and dried to 11% moisture content and the crack is cutting in Radial-Longitudinal system.
Near Infrared Spectroscopy as a Tool for Estimation of Mechanical Stresses in Wood
Authors: Sandak Jakub , Sandak Anna , Pauliny Dusan , Krasnoshlyk Victoria , Hagman Olle
Published: September 2013

Significant scientific work has been dedicated for exploration of the infrared applications within wood science and technology, not much has been done linking it to the mechanical testing. It is expected that due to mechanical stresses (and related deformations) the interaction between constitutive elements of wood changes, proportionally to the stresses applied. The response of the material to mechanical stresses (such as tensile loading) on the molecular level should be therefore detectable by means of infrared spectroscopy. Dedicated tests have been devoted for proving this hypothesis. Self-developed testing machine has been integrated with infrared spectrometer in order to conduct a series fully controlled mechanical tests. It was possible to predict stress level of wood during tension by applying proper chemometric analysis (partial least square (PLS) models). Implementation of infrared spectroscopy in to timber engineering and mechanical testing of wood provides very essential supplement to the typical information collected during standard tests. More additional tests and reference data is necessary in order to create more reliable and universal model suitable for routine assessments. Nevertheless, it was demonstrated that prediction of the stress on the basis of the infrared spectra is possible.
Stress Level Prediction in Axially-Loaded Timber Beams Using Resonance Frequency Analysis: A Pilot Study
Authors: Lechner Thomas , Laux Steve , Sandin Daniel
Published: September 2013

The structural integrity due to problems in the uncertainties of load, the load-carrying capacity of timber structures is of great importance, since peaks of increased loads might occur. One solution of these problems lies in the evaluation of timber structures using non-destructive testing (NDT) methods, and in this special case frequency based identification methods. The aim of this paper was to investigate if it is possible to estimate the axial loads in timber beams using resonance frequency analysis to evaluate on whether the beams have sufficient load-bearing capacity. This was achieved by performing transversal frequency measurements on 32 timber specimens and an aluminium bar under tension. The latter hereby served as a homogeneous reference for better interpretation of results. The two first frequencies, together with different values for the E-modulus were then used to estimate the axial load S and the rotational stiffness k at the boundaries. The stress levels for the timber ranged from 2 MPa to 11 MPa, whereas for the aluminium reference bar the frequencies were measured for stress levels from 4 MPa to 32 MPa. The numerical model behind the calculations was based on Timoshenko beam theory, including effects of shear deformations and rotary inertia. Finally, a sensitivity analysis was carried out to investigate the influence of errors in input parameters on the final results. The best results were obtained using the E-modulus derived from transversal vibration tests and showed a mean error ranging from 7.6% to 46.6%, where the results generally improved for higher loads. The results of the sensitivity analysis showed that the sensitivity of the estimated axial load decreases for higher stress levels, which could also be observed in the test results. The most influential parameters on the quality of the results were the measured frequencies and the clear beam length, followed by the density and the E-modulus.
A New Method to Assess the Seismic Vulnerability of Existing Wood Frame Buildings
Authors: Loss Cristiano , Piazza Maurizio , Zonta Daniele
Published: September 2013

This paper aims at applying a direct displacement-based method to assess the seismic vulnerability of existing multi-storey wooden buildings. This procedure is consistent with Priestley’s direct methodology firstly developed for reinforced concrete structures. The distinctive characteristic of the proposed method is that the system response is quantified through the use of displacements instead of equivalent elastic strengths, according to the traditional force-based approaches. Consequently, in comparison to common force-based procedures, this method cannot only be considered as a rational alternative but also as a new seismic philosophy to design or assess structures. A representative timber construction system commonly used in Italy was selected as case study. The construction system illustrated in this work was analysed in detail, with special attention given to the mechanical connections typically used. The typical failure mechanisms and the energy dissipation capacity of the structure or of its members were identified on the basis of the mechanical properties of structural parts and connections, as well as of their geometry. In the proposed direct displacement-based assessment approach, the seismic intensity that would cause the limit state to be exceeded can be calculated by means of simple formulas. Therefore, the capacity to demand ratio can be simply derived. The procedure could be used to gauge the likelihood of losses, by combining it with simple loss models to account for probabilistic aspects.
Numerical Modelling of Historic Vaulted Timber Structures
Authors: Ferreira Carina Fonseca , D’Ayala Dina , Fernandez Cabo Jose L. , Díez Rafael
Published: September 2013

Historic timber structures forming vaulted roofs of public and ecclesiastical buildings are present worldwide. The structural response of these constructions is usually governed by the structural performance of the joints, the interaction between the timber structure and the masonry parts, and the current condition of both joints and timber members. At present, numerical approaches, such as finite element method-based approaches are well-established tools for investigating the global response of complex historic structures. Using a FE-based software package, the authors developed a numerical model of a portion of an existing historic vaulted timber structure, which is part of the roof of the Cathedral of Ica in Peru, considering the in-plane semi-rigid response of the planked arches in the elastic range. For this purpose, the rotational and shear stiffness of the joints and the properties of the materials, which are assumed in good conditions, are calibrated by comparing the numerical outputs with experimental results available in literature. The aim of the work presented here is to compare the response of the same vault assuming either continuous (planks continuously connected) or discontinuous arches (modelling of the semi-rigid response of the joints which connect the planks together).
Bending Tests on Natural Fiber Reinforced Fir Wooden Elements
Authors: Borri Antonio , Corradi Marco , Speranzini Emanuela
Published: September 2013

This paper gives the results of an experiment on timber elements reinforced in the tension zone through the application of strips of natural flax, hemp, bamboo and basalt fibers, creating different arrangements and using different quantities. The testing consisted of several stages that concerned wood rafters and beams of low and good quality. The wooden elements were subjected to bending tests that made it possible to measure the increase in capacity and stiffness resulting from the composite reinforcement.
Durability of Wooden Member Reinforced by Carbon-Fiber
Authors: Hojo Tetsuo
Published: September 2013

Durability on structural function of a carbon fiber reinforced member was evaluated with various environment tests. In this research, the relations between the environmental factor, such as the temperature and humidity, and the strength properties were analyzed firstly using heat cycle test and natural exposure test. Durability was analyzed from the viewpoint of the strength deterioration in the bonded part. A mechanism of deterioration for the decrease of the bond strength to influence the decrease in the bending strength was indicated. Finally, an evaluating method of carbon fiber reinforcement was shown through this study.