• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 141
  • 132
  • 55
  • 32
  • 10
  • 8
  • 4
  • 4
  • 4
  • 3
  • 3
  • 2
  • 2
  • 1
  • 1
  • Tagged with
  • 419
  • 105
  • 67
  • 66
  • 64
  • 55
  • 51
  • 48
  • 46
  • 42
  • 40
  • 39
  • 38
  • 38
  • 36
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
111

Behavior of Wood Exposed to Fire: A Review and Expert Judgement Procedure for Predicting Assembly Failure.

Bland, Kenneth Edward 10 February 2005 (has links)
This paper summarizes research on the structural perfomance of wood elements and assemblies exposed to fire and reviews methodologies available to predict performance. This reasecrh provides a wealth of information on topics such as how fast a flame spreads across the surface of wood, how much smoke is produced during combustion and at what rate does wood char and at what heat release rate.
112

Prevalência de white striping e wooden breast em frangos de corte suplementados com níveis crescentes de lisina na fase de crescimento ou final / Prevalence of white striping and wooden breast in broilers fed diets with increasing lysine levels in grower or finisher phase

Cruz, Rafael Fontana Abs da January 2016 (has links)
Foram conduzidos dois experimentos para avaliar a prevalência e severidade das lesões de white striping (WS) e wooden breast (WB) em peitos de frangos alimentados com níveis crescentes de lisina digestível (Lis dig.) de 12 a 28 dias (Exp. 1) e de 28 a 42 dias (Exp. 2).Os testes foram conduzidos utilizando machos Cobb x Cobb 500 de empenamento lento com 1 dia de idade, ambos com 6 tratamentos e 8 repetições cada. O aumento da Lis dig. foi igualmente espaçado de 0,77 a 1,17% no Exp. 1 e de 0,68 a 1,07% no Exp. 2. A dieta com nível mais baixo de Lis dig. não foi suplementada com L-Lisina no experimentos e todos os outros aminoácidos (AA) essenciais estão de acordo ou excedem em até 5% as recomendações comerciais, a fim de não limitar o crescimento das aves. Foram selecionadas aleatóriamente quatro aves por repetição e processadas aos 35 e 42 dias nos Exp. 1 e 2, respectivamente. Os peitos desossados foram submetidos a avaliação de 3 pessoas para detectar a presença de WS e WB assim como fornecer os escores de WS (0-normal, 1-moderao, 2-severo) e WB (0-normal, 1-moderado leve, 2-moderado, 3-severo). O aumento da Lis dig. apresentou efeito positivo no peso vivo, peso da carcaça e peito bem como no rendimento de peito. A prevalência de WS e WB foi 32,3 e 85,9% no Exp. 1 e 87,1 e 89,1% no Exp. 2. Aves submetidas a dieta sem suplementação de Lis apresentaram os menores escores médios de WS e WB (0,22 e 0,78 no Exp. 1 e 0,61 e 068 no Exp. 2). Respostas lineares foram obtidas através das variáveis de desempenho para WS e WB no Exp. 1, enquanto que a resposta para as variáveis no Exp. 2 foram quadráticas. O aumento dos níveis de Lis melhora o desempenho zootécnico e as caracteristicas das carcaças, além de induzir a ocorrência e severidade das lesões de WS e WB, devido, provavelmente, aos níveis de Lis que maximizam o potencial genético para crescimento e rendimento de peito. / Two experiments were conducted to evaluate the prevalence and severity of white striping (WS) and wooden breast (WB) in breast fillets from broilers fed diets with increasing digestible lysine (dig. Lys) from 12 to 28 d (Exp. 1) and from 28 to 42 d (Exp. 2). Trials were sequentially conducted using 1-d-old slow feathering Cobb × Cobb 500 male broilers, both with 6 treatments and 8 replicates each. Increasing dig. Lys levels were equally spaced from 0.77 to 1.17% in Exp. 1 and from 0.68 to 1.07% in Exp. 2. The lowest dig. Lys diet was not supplemented with L-Lys in either one of the studies and all other essential amino acids (AA) met or exceeded current commercial recommendations such that their dietary concentrations did not limit broiler growth. Four birds per pen were randomly selected from each replication and processed at 35 and 42 d in Exp. 1 and Exp. 2, respectively. Deboned breast fillets were submitted to a 3 subject panel evaluation to detect the presence of WS and WB as well as to provide scores of WS (0-normal, 1-moderate, 2-severe) and WB (0-normal, 1-moderate light, 2-moderate, 3-severe). Increased dig. Lys had a positive effect on body weight, carcass and breast weight as well as breast yield. White striping and WB prevalences were 32.3 and 85.9% in Exp 1 and 87.1 and 89.2% in Exp 2. Birds fed diets not supplemented with Lys had the lowest average WS and WB scores (0.22 and 0.78 in Exp. 1 and 0.61 and 0.68 in Exp. 2). White striping and WB presented linear responses to performance variables in Exp 1, whereas quadratic responses were observed for all variables in Exp 2. In conclusion, increasing Lys levels improved growth performance and carcass traits and induced the occurrence and severity of WS and WB lesions probably due to dig. Lys dietary levels that maximized the genetic potential for growth and breast meat yields.
113

走馬樓三國吳簡書法硏究: 以嘉禾吏民田家莂為對象. / Study of the calligraphy of the Wu Wooden tablets from Zoumalou: the "bie" tablets of the Jiahe period / "Bie" tablets of the Jiahe period / Zoumalou san guo Wu jian shu fa yan jiu: yi jia he li min tian jia bie wei dui xiang.

January 2001 (has links)
洪娟. / "2001年6月" / 論文 (哲學碩士)--香港中文大學, 2001. / 參考文獻 (leaves [65-71]) / 附中英文摘要. / "2001 nian 6 yue" / Hong Juan. / Lun wen (zhe xue shuo shi)--Xianggang Zhong wen da xue, 2001. / Can kao wen xian (leaves [65-71]) / Fu Zhong Ying wen zhai yao. / Chapter 第一章 --- 緒言 / Chapter 第一節 --- 簡牘硏究槪況 / Chapter 一 --- 出土情況 --- p.1 / Chapter 二 --- 簡牘書法硏究成果 / Chapter (一) --- 中國學者的簡牘書法研究 / Chapter 1. --- 八十年代及以前的硏究 --- p.2 / Chapter 2. --- 九十年代及以後的硏究 --- p.7 / Chapter (二) --- 曰本及西方學者的簡牘書法研究 --- p.10 / Chapter 第二節 --- 走馬樓吳簡書法硏究前瞻 / Chapter 一 --- 走馬樓吳簡的性質 --- p.14 / Chapter 二 --- 吳簡書法的研究方法 --- p.15 / Chapter 第二章 --- 走馬樓吳簡書法硏究 / Chapter 第一節 --- 三國書體發展槪況 --- p.22 / Chapter 第二節 --- 從偏旁分析探討吳簡的書體 / Chapter 一 --- 篆書 --- p.25 / Chapter 二 --- 隸書 --- p.26 / Chapter (一) --- 受碑別字影響的寫法 --- p.27 / Chapter (二) --- 相對於碑別字較統一的字形 --- p.30 / Chapter (三) --- 對於字形的改造 --- p.31 / Chapter 三 --- 楷書 / Chapter (一) --- 改造隸書字形 --- p.32 / Chapter (二) --- 對於隸書筆法的改造 --- p.33 / Chapter 四 --- 草書 --- p.36 / Chapter 第三章 --- 從吳簡看三國書風 / Chapter 第一節 --- 與鍾繇書跡的比較 / Chapter 一 --- 鍾繇書風 --- p.40 / Chapter 二 --- 吳簡的書手 --- p.41 / Chapter 三 --- 吳簡與鍾書比較 --- p.43 / Chapter 第二節 --- 三國書風的展現 / Chapter 一 --- 三國書風綜述 --- p.47 / Chapter 二 --- 吳簡對於三國書法面貌的展現 --- p.51 / 結語 / Chapter 一 --- 走馬樓吳簡書法研究的意義 --- p.58 / Chapter 二 --- 相關問題的探討 --- p.60 / Chapter 三 --- 硏究展望 --- p.61 / 參考書目 / 附錄一:近世簡牘帛書出土年表 / 附錄二:吳簡對照字形表 / 圖版
114

Marketingová strategie firmy Haas Fertigbau s.r.o. na zahraničních trzích / Marketing strategy of the company Haas Fertigbau on the foreign markets

Strolená, Jana January 2011 (has links)
The main aim of this thesis is an introduction of the company Haas Fertigbau, which is concerned with construction of wooden houses and after that making of a marketing strategy. This thesis is diveded into three main parts. In the first part of this thesis is analyzed the current situation of the timber industry and of the building. These two fields that like every others were affected by the global economic crisis. In the next part it is introduced a parent company Haas Fertigbau and afterwards there is in great detail described the company Haas Fertigbau based in Chanovice. In the last chapter there is a practical part of this thesis. It contains a partial approximation of the current marketing strategy, a proposal for a comprehensive marketing strategy and a number of recommendations which could be an inspiration for the company into the future.
115

Caracterização e avaliação do fluxo produtivo de habitação em madeira de plantios florestais segundo indicadores de sustentabilidade: consumo de energia e resíduos gerados / not available

Barbosa, Juliana Cortez 23 October 2003 (has links)
O setor da construção civil é hoje considerado não somente o maior consumidor de recursos e energia, mas também o maior gerador de resíduos nos centros urbanos. Uma reformulação no setor faz-se necessária para a melhoria dos processos de produção e prevenção dos efeitos da poluição. Estas mudanças são essenciais para que se desenvolvam tecnologias construtivas mais limpas e mais eficientes, que reduzam os impactos ao meio ambiente através de um uso mais racional dos recursos naturais (com menor consumo energético e diminuição dos resíduos gerados), minimizando o desperdício de matéria-prima já escassas. Este trabalho foi realizado a partir de dados coletados em 10 serrarias que processam madeira serrada de pinus na região administrativa de Sorocaba. Nesta região concentra-se atualmente o maior potencial madeireiro do Estado de São Paulo, 42,3% de toda a área de florestas plantadas do Estado, sendo também o maior centro produtor de pinus do Estado, com 58,5%. Esses dados foram convertidos para o cálculo do consumo energético no processamento do eucalipto. Dada a relevância do consumo de energia e a quantidade de entulhos gerados pelo setor da construção civil, o presente trabalho tem como objetivo analisar, dentro da cadeia produtiva da madeira serrada, o consumo energético e os resíduos gerados na produção de componentes construtivos utilizados em painéis de vedação para casas de madeira. Foram analisadas peças de seções comerciais utilizadas em três tipos diferentes de painéis. Dois destes sistemas pré-fabricados, executados na cidade de São Carlos - SP, possuem sistema estrutural em madeira serrada de eucalipto com paredes duplas de pinus. Um deles possui na face interna, lambri e, na externa, deck horizontal, enquanto o outro sistema construtivo possui na face interna, lambri e, na face externa, tábua mata-junta. O terceiro sistema de vedação, construído em Campos do Jordão - SP, é composto por estrutura em pórticos de madeira serrada de pinus com paredes externas de fechamento duplo de lambri de 2,2 cm de espessura. A parede interna é simples com apenas uma camada de lambri de igual espessura. O consumo de energia foi medido para cada tipologia de painel construído, calculando-se o número de operações de corte e a potência de cada equipamento envolvido. Os resíduos gerados foram obtidos a partir do cálculo da área de material particulado removido. O índice de desempenho energético foi aferido em kWh por metro quadrado de painel (energia) e em metros cúbicos por metro quadrado de painel (resíduo). Estes resultados poderão vir a ser comparados com diferentes materiais de construção utilizados em sistemas de vedação, assim como fornecer informações para análise do grau de sustentabilidade na produção de um edifício de madeira em relação ao consumo energético. / The civil construction sector today is considered not only the greatest consumer of material and energy resources in urban centres, but also a major generator of waste. The sector needs a reformulation for the improvement of production and for the prevention of pollution. It is therefore essential to consider cleaner and more efficient technological processes, i. e., to decrease environmental impacts through a more rational use of resources (with lower consumption of energy anbd less production-related waste), minimizing the squandering of scarce resources. The study reported on here was based on data collected from ten pine sawmills in the region of Sorocaba, state of São Paulo, Brazil. This region currently possesses the greatest potential for sawed wood in the state of São Paulo, 42.3% of all the forest planted in State, and is the state\'s largest pinewood producer, about 58.5%. Those datas were also aplicated to calculate the energy consumed for sawn eucalyptus pieces. Given the relevance of energy consumption and the quantity of produced rubbish by the construction sector, the purpose of this work is to analyse the consumption of energy and the produced waste in the productive cycle of boards for wooden housing, from the cutting stage, processing, and prefabrication of componentes to the assembly of wall panels. This study involved wooden boards of commercial dimensions applied in three different types of panelling in three buildings. Two of theseprefabricated systems, executed in the city of São Carlos, have a structural system made of sawn eucalyptus wood with double walls of pine. One of them is lined internally with wainscoting and externally with horizontal decking, while the other system has internal wainscotting and external match boarding. The third system, built in Campos de Jordão, is composed of a structural framework of sawed pine, with external double shutter walls of 2.2 mm match boarding and simple internal walls consisting of a single layer of 2.2 mm thick match boarding. The consumption of energy was measured for each kind of board produced, calculated from the number of cutting operations and the power of each machines involved. The produced waste was calculated by the area of removed particulate material. The energy performance index were expressed in kWh consumed per square meter of wood panel produced (enegy) and in m3 produced per square meter of wood panel produced (waste). These data will serve as the basis for a comparison with various types of construction materials used in wall systems (concrete, brick and others), and provide information for the analysis of the sustainability of wooden construction systems from the standpoint of energy consumption.
116

Comparison of Methods for Detection of Listeria on Wooden Shelves used for Cheese Aging: Challenges Associated with Sampling Porous Surfaces

Frontino, Gina Christine 01 January 2019 (has links)
This thesis examined the efficacy of various sampling and detection methods used for environmental monitoring of Listeria species on wooden surfaces used for cheese aging. Government agencies including the Food and Drug Administration (FDA) and United States Department of Agriculture (USDA) recommend enrichment methods coupled with use of environmental sponges and swabs. Our study compared efficacy of sponge swabs manufactured by 3M™ and World Bioproducts. There is a lack of research validating the best performing swab type and enrichment method combination that is sensitive when used on rough, porous surfaces. The sensitivity of these environmental sampling tools and methods are critical considerations to effectively monitor the presence of Listeria species on wooden boards used during aging of artisan cheese. Seasoned spruce wooden shelves, cut into 100cm2 replicates, were spot inoculated with varying concentrations of Listeria species inocula, the Listeria species strains consisted of two L. monocytogenes strains and a Green Florescence Protein (GFP) expressing strain of L. innocua. The inoculated wooden surface was swabbed with three environmental sampling sponge/swab formats (World Bioproducts© EZ ReachTM environmental swabs (WBEZ) with HiCap (WBHC) and Dey-Engley (WBDE) neutralizing broths; and 3MTM environmental swabs (3MTM) with Dey-Engley neutralizing broth). Enumeration methods were used to determine the low target limits of detection. Once the low target concentrations were identified, five enrichment methods consisting of 3MTM Listeria Environmental Plate, FDA, Dual Enrichment, modified USDA, and modified FDA were challenged against low concentrations of Listeria species inocula (0.01 cfu/cm2, 0.1 cfu/cm2, 1 cfu/cm2) and the three environmental sponge swab formats. Performance of the swab formats was assessed by collection of naturally contaminated environmental samples (n=405) from dairy farm environments, swabbing where wooden surfaces existed, and analyzed using the most effective enrichment methods found from previous experiments. Lastly, the wooden surfaces and sponge swabs were observed under a Florescent Microscope using GFP L. innocua to visually determine how each sponge material of the 3M™ and World Bioproducts recovered the inocula. When wood surfaces were inoculated at high concentration levels of Listeria spp., all swab formats performed equally for detecting Listeria. Success of positive recovery at low concentrations was variable, where enrichment methods and swabs were not dependent on each other. The swab format that worked best for detecting low levels of Listeria species was the WBDE sponge swab. The WBDE swab also performed the best in dairy farm environmental sampling. The m-USDA enrichment method was found to be most effective in recovery and repair of low and potentially injured Listeria spp. Wooden surfaces are rough and porous and should be taken into consideration when creating an environmental sampling plan for these food contact surfaces. All swabs and methods performed with only slight variation, but the variation could be significant when monitoring wooden shelves with low level contamination of Listeria species. Artisan cheesemakers who use wooden shelves during the aging of their cheese, should ensure use of the most sensitive detection methods.
117

Development of rapid visual screening tool for seismic evaluation of wood-frame dwellings

Lucksiri, Kraisorn 21 March 2012 (has links)
During the past several decades, earthquakes have caused extensive damage to buildings, including wood-frame, single-family dwellings, in the United States. In order to mitigate future losses, existing buildings in earthquake prone areas should be evaluated for their seismic safety. This is also an important issue for buildings in Oregon due to the Cascadia subduction zone along its west coast. One seismically vulnerable element observed in wood-frame, single-family dwellings is the shear walls. In general, assessment of shear wall seismic performance can be accomplished by a building-specific engineering calculation. Extra effort is required if the effects of plan irregularity are a concern. This project aims to facilitate seismic evaluation of wood-frame dwellings by proposing a new engineering-based rapid visual screening method to examine the expected performance level of the structure's exterior shear walls to resist lateral forces from ground motions, including torsional forces induced from plan irregularity. In order to achieve the objective, SAPWood software was used to perform a series of nonlinear time-history analyses for 480 representative models, covering different combinations of shape parameters and shear wall opening-related parameters. The evolutionary parameter hysteresis model was used to represent the load-displacement relationship of structural panel-sheathed shear walls and a ten parameter CUREE hysteresis model for gypsum wallboard sheathed walls. The calculated maximum lateral drifts were used as basic information for the development of the new method. Through the development process, the significance of both plan configuration and shear wall openings were emphasized as they affect the overall seismic performance of a building through building mass, lateral stiffnesses, and eccentricities. Within the study range, single-family dwellings with two stories, a larger percentage of openings, and having a garage door were shown to be more vulnerable to seismic events. Plan configuration and shear wall openings were important features especially in houses located in high 1 (0.5g ≤ S[subscript a] < 1.0g) and high 2 (1.0g ≤ S[subscript a] < 1.5g) seismicity regions, as they could potentially lead to severe damage. For low and moderate seismicity, the performance ranges from satisfying the collapse prevention limit to the immediate occupancy limit. The developed piRVS (plan irregularity Rapid Visual Screening) takes into consideration the shape of the floor plan, number of stories, base rectangular area, percent cutoff, and openings from doors/windows and garage doors, and supports evaluation at the immediate occupancy (IO), life safety (LS), and collapse prevention (CP) performance levels. The piRVS provides relatively more conservative assessment results than FEMA 154 and ASCE 31 Tier 1. Its prediction for the two applicable Northridge earthquake damage samples is reasonable. This method will help architects, engineers, building officials, and trained inspectors in examining the expected seismic performance of shear walls, considering the effects of plan irregularity in wood-frame, single-family dwellings / Graduation date: 2012
118

Performance-based seismic design of light-frame shearwalls

Kim, Jun Hee 22 December 2003 (has links)
Performance-based design has gained interest in recent years among structural designers and researchers. Performance-based design includes selection of appropriate building sites, structural systems and configurations, as well as analytical procedures used in the design process, to confirm that the structure has adequate strength, stiffness and energy dissipation capacity to respond to the design loads without exceeding permissible damage states. Although performance-based seismic design has advanced for some materials and structural types, such as steel and reinforced concrete buildings and bridges, its application to light-frame structures remains largely unexplored. The objective of this research was to explore the potential for the application of performance-based engineering concepts to the design and assessment of woodframe structures subject to earthquakes. Nonlinear dynamic time-history analysis was used to predict the performance of shearwalls considering a suite of scaled characteristic ordinary ground motions to represent the seismic hazard. Sensitivity studies were performed to investigate the relative effects of damping, sheathing properties, fastener type and spacing, panel layout, and other properties on the performance of wood shearwalls. In addition, the effects of uncertainty in ground motions and variability in sheathing-to-framing connection hysteretic parameters were investigated. Issues such as the contribution of nonstructural finish materials, different seismic hazard regions, and construction quality also were investigated and modification factors to adjust peak displacement distributions were developed. The peak displacement distributions were then used to construct performance curves and design charts as a function of seismic weights for two baseline walls. Finally, fragility curves were developed for the baseline walls considering different nailing schedules, corresponding allowable seismic weights, and various overstrength (R) factors. / Graduation date: 2004
119

Evaluation of remediation techniques for circular holes in the webs of wood I-joists

Polocoser, Tiberiu 12 June 2012 (has links)
The objective of this project was to evaluate methods to remediate a wood I-joist with a single, circular hole in the web while leaving utilities in place. The methods were experimentally evaluated with a full-scale bending test using four equally spaced point loads. There were three depths of joists with varying flange widths and two span lengths (4.88 m & 2.44 m). Failure modes for the long span joists without holes were in the flanges in either tension, compression or lateral buckling; but once a hole was introduced the majority were classified as shear failures. Effectiveness of the remediation was evaluated based on three criteria: strength, stiffness, and ease of installation/cost. The OSB collar patch was effective for 8 out of the 12 series tested. A maximum reduction of load from a joist with no hole to one with a hole was 49% for the long span and 58% for the short span. The OSB collar was not as effective in returning stiffness to the joists, but was easier to install and less expensive than the LSL patch. / Graduation date: 2013
120

Model calibration of a wooden building block / Kalibrering av materialparametrar för byggnadselement i trä

Karim, Ali Abdul Jabbar, Lessner, Johan, Moridnejad, Mehrdad January 2013 (has links)
Constructing multi floor buildings by light weight material have increased recently. There are many advantages of using light weight material, such as wood, for the environment. However, one of the deficiencies of lightweight material is the acoustic performance. Transmission of sound and vibration through floors in multi floor buildings in wood is a drawback to be considered. There are many studies that have addressed this issue. It is most common to make a finite element models well as experiments in laboratory. In these studies the material properties in the FE model are probably often adjusted to correlate to the laboratory experiments, since there is a large spread in material properties found in literature. This thesis however tries to elaborate on the actual material properties of the included wooden elements. Dynamic testing is done to determine the spread (here spread means gap between material properties) in material properties of wooden elements. The materials tested are chipboards and two types of wooden beams. The examined beams are both normal wooden beams and laminated veneer lumber beams. When the dynamic behaviour is known for the wooden parts, they are assembled to two small floor systems. The floor systems consist of four beams and one wooden board. The assembly is dynamically tested in laboratory and in FE software. The FE model used the known material properties for each individual building part. The results from the FE model correlate well with the laboratory tests. This shows that when material properties are known a FE model can predict the real behaviour. However, the examined material properties show a large spread from beam to beam, etc and a better knowledge about the material properties of used wooden parts is needed. / Att bygga flervåningshus med lätta byggmaterial har blivit allt vanligare. Det finns många fördelar med att använda lätta material, såsom trä. En av fördelarna är att det är skonsamt för miljön. Emellertid är en av bristerna i lättviktsmaterial den akustiska prestandan. Överföring av ljud och vibrationer genom golv i flervåningshus i trä är en nackdel att överväga. Det finns flera studier som har behandlat denna fråga. Ofta görs finita element modeller samt tester i laboratorium. I dessa studier justerar man materialegenskaperna i FE-modellen för att korrelera mot laboratorieexperiment. Detta eftersom det finns en stor spridning i materialegenskaperna för trä i litteraturen. Med detta examensarbete, undersöks de faktiska materialegenskaperna hos träelementen genom försök. Dynamiska tester utförs för att bestämma spridningen i materialegenskaper. De testade materialen är spånskivor och två typer av träbalkar. De undersökta balkarna är både normala träreglar och laminerade faner balkar. När det dynamiska beteendet är känt för trädelarna, monteras de ihop till två små golvsystem. Golvsystemen består av fyra balkar och en träskiva. Den assemblerade modellen testas både dynamiskt i ett praktiskt försök och i ett FE program. I FEmodellen används de tidigare framtagna faktiska materialegenskaper för varje ingående enskild byggnadsdel. Resultaten från FE-modellen korrelerar väl med de praktiska experimenten. Med detta examensarbete visas att när materialegenskaperna är kända kan FE-modellen förutsäga det verkliga beteendet. De undersökta materialegenskaperna visar dock en stor spridning från balk till balk, etc. och mer kunskap om materialegenskaper hos trädelar behövs.

Page generated in 0.1258 seconds