BAALISAMPANG T , ABBASSI R , GARANIYA V , et al . Review and analysis of fire and explosion accidents in maritime transportation [J ] . Ocean Engineering , 2018 , 158 : 350 - 366 . DOI: 10.1016/j.oceaneng.2018.04.022 http://doi.org/10.1016/j.oceaneng.2018.04.022 https://linkinghub.elsevier.com/retrieve/pii/S0029801818304542 https://linkinghub.elsevier.com/retrieve/pii/S0029801818304542

TARVER C M , TRAN T D . Thermal decomposition models for HMX-based plastic bonded explosives [J ] . Combustion and Flame , 2004 , 137 ( 1 ): 50 - 62 . DOI: 10.1016/j.combustflame.2004.01.002 http://doi.org/10.1016/j.combustflame.2004.01.002 https://linkinghub.elsevier.com/retrieve/pii/S0010218004000215 https://linkinghub.elsevier.com/retrieve/pii/S0010218004000215

HENSON B F , ASAY B W , SANDER R K , et al . Dynamic measurement of the HMX β - δ phase transition by second harmonic generation [J ] . Physical Review Letters , 1999 , 82 ( 6 ): 1213 - 1216 . DOI: 10.1103/PhysRevLett.82.1213 http://doi.org/10.1103/PhysRevLett.82.1213 https://link.aps.org/doi/10.1103/PhysRevLett.82.1213 https://link.aps.org/doi/10.1103/PhysRevLett.82.1213

ENGLERT-ERICKSON M A , HOLMES M D , PARKER G R , et al . Gas transport in the insensitive high explosive PBX 9502 [J ] . Propellants, Explosives, Pyrotechnics , 2020 , 45 ( 6 ): 942 - 949 . DOI: 10.1002/prep.v45.6 http://doi.org/10.1002/prep.v45.6 https://onlinelibrary.wiley.com/toc/15214087/45/6 https://onlinelibrary.wiley.com/toc/15214087/45/6

SCHMITT R G , BAER T A . Millisecond burning of confined energetic materials during cookoff:SAND-97-2668C;CONF-9710108 [R/OL ] . Albuquerque, NM , US : Sandia National Lab. , https://www.osti.gov/biblio/548611 https://www.osti.gov/biblio/548611 https://www.osti.gov/biblio/548611.

ASAY B W . Cookoff[M/OL]//Shock Wave Science and Technology Reference Library, Vol. 5: Non-shock Initiation of Explosives . Berlin, Heidelberg,Germany : Springer , 2010 : 403 - 482 .[2021-11-13 ] . https://DOI.org/10.1007/978-3-540-87953-4_7 https://DOI.org/10.1007/978-3-540-87953-4_7 https://DOI.org/10.1007/978-3-540-87953-4_7. DOI: 10.1007/978-3-540-87953-4_7 https://dx.doi.org/10.1007/978-3-540-87953-4_7 .

HILL L G . Classical theory of thermal criticality [M/OL ] // ASAY B W.Shock Wave Science and Technology Reference Library, Vol. 5:Non-shock Initiation of Explosives.Berlin, Heidelberg,Germany:Springer , 2010 : 129 - 243 .[2021-10-12 ] . https://DOI.org/10.1007/978-3-540-87953-4_4 https://DOI.org/10.1007/978-3-540-87953-4_4 https://DOI.org/10.1007/978-3-540-87953-4_4. DOI: 10.1007/978-3-540-87953-4_4 https://dx.doi.org/10.1007/978-3-540-87953-4_4 .

MCGUIRE R R , TARVER C M . Chemical-decomposition models for the thermal explosion of confined HMX, TATB, RDX, and TNT explosives: UCRL-84986;CONF-810602-15 [R/OL ] . CA,US:Lawrence Livermore National Lab. , 1981 .[2021-11-13 ] . https://www.osti.gov/biblio/6532473 https://www.osti.gov/biblio/6532473 https://www.osti.gov/biblio/6532473.

刘瑞峰 , 王昕捷 , 黄风雷 , 等 . 2,4-二硝基苯甲醚基熔铸炸药宏细观烤燃响应特性数值分析 [J ] . 兵工学报 , 2022 , 43 ( 2 ): 287 - 296 .

LIU R F , WANG X J , HUANG F L , et al . Macro-meso-scale Cook-off Simulations of DNAN-based melt-cast explosives [J ] . Acta Armamentarii , 2022 , 43 ( 2 ): 287 - 296 . (in Chinese) DOI: 10.3969/j.issn.1000-1093.2022.02.006 http://doi.org/10.3969/j.issn.1000-1093.2022.02.006 The melting of DNAN and the phase transformation of HMX crystal occur in 2,4-dinitroanisole (DNAN)/octogen (HMX) melt-cast explosives during cook-off test. A melting reaction kinetics model is developed for DNAN, and a four-step reaction kinetics model of HMX is used to study the melting, phase transformation and ignition response of DNAN-based melt-cast explosives at the macro-meso scale. Macroscale calculation shows that DNAN melts at about 377.00 K, HMX undergoes a phase transformation at about 450.00 K, and the ignition temperature is 531.34 K. The ignition position locates at the annular area between the upper and lower ends and the side of the explosive, the error between the calculated and experimental ignition times is 0.5%. The mesoscale calculation results based on the macroscopic ignition area show that the ignition position locates at HMX crystal, and the evolution rules of DNAN melting and HMX phase transformation are obtained: at different times, the statistical distribution of liquid-phase DNAN is U-shaped, and δ-HMX is approximately normal. The macro-meso scale cook off simulations of DNAN-based melt-cast explosives are of great significance for understanding the thermal ignition mechanism of energetic materials.

张海军 , 聂建新 , 王领 , 等 . 端羟基聚醚推进剂慢速烤燃尺寸效应 [J ] . 兵工学报 , 2021 , 42 ( 9 ): 1858 - 1866 . DOI: 10.3969/j.issn.1000-1093.2021.09.006 http://doi.org/10.3969/j.issn.1000-1093.2021.09.006 为分析结构尺寸对端羟基聚醚推进剂发动机慢速烤燃响应特性的影响，开展了仿真计算研究。模拟不同直径和长径比发动机在慢速烤燃条件下的响应过程，分析慢速烤燃过程中推进剂的温度分布，以及反应温度、反应时间和反应位置随发动机直径和长径比的变化规律。建立一种基于图像处理的高温推进剂质量分布计算方法，计算慢速烤燃条件下发动机反应前推进剂的温度分布，并将其作为评价发动机慢速烤燃反应剧烈程度的参量。研究发现：直径大小对慢速烤燃响应时间和响应温度影响较大，长度影响较小；二者对反应位置影响都较大，随着尺寸和长径比的增大，反应位置向装药边缘移动，当尺寸较大时反应位置与壳体边缘的距离保持稳定；高温推进剂的质量占比随着长径比改变而发生变化，在装药量分别为5.5 kg、18.0 kg及44.0 kg烤燃件中，当装药直径在150~160 mm时，3种烤燃件发生反应前的高温推进剂占比最小。

ZHANG H J , NIE J X , WANG L , et al . Numerical simulation on size effect of hydroxyl terminated polyether propellant engine during slow cook-off [J ] . Acta Armamentarii , 2021 , 42 ( 9 ): 1858 - 1866 . (in Chinese) DOI: 10.3969/j.issn.1000-1093.2021.09.006 http://doi.org/10.3969/j.issn.1000-1093.2021.09.006 The response processes of hydroxyl terminated polyether (HTPE) propellant engines with different sizes and length-to-diameter ratios were simulated to analyze the effect of structure size on their slow cook-off response characteristics. The temperature distribution, reaction temperature, reaction time and reaction location of propellant were studied. A calculation method based on image processing is established to calculate the temperature distribution of propellant before reaction of motor under slow cook-off. The temperature distribution is used as a parameter to evaluate the response intensity of slow cook-off. The results show that the engine diameter has a great influence on the reaction time and temperature of slow cook off, while the engine length has little effect on them. Both of them have great influence on the reaction position. With the increase in the size and length-to-diameter ratio, the reaction position moves to the edge of the charge. When the size is large enough, the distance between the reaction position and the shell edge remains stable. The mass ratio of high temperature propellant changes with the change of length-to-diameter ratio. When the charge diameter is 150-160 mm, the proportion of high temperature propellant before reaction is the smallest with charges of 5.5 kg, 18.0 kg and 44.0 kg, respectively.

HILL L G . Burning crack networks and combustion bootstrapping in cook-off explosions [J ] . AIP Conference Proceedings , 2006 , 845 ( 1 ): 531 - 534 .

段卓平 , 白志玲 , 白孟璟 , 等 . 强约束固体炸药燃烧裂纹网络反应演化模型 [J ] . 兵工学报 , 2021 , 42 ( 11 ): 2291 - 2299 . DOI: 10.3969/j.issn.1000-1093.2021.11.001 http://doi.org/10.3969/j.issn.1000-1093.2021.11.001 为表征受约束装药非冲击点火后的反应演化行为，建立了燃烧裂纹网络反应演化理论模型。该模型量化了反应烈度，通过与实验结果对比验证了模型的适应性。结果表明：壳体约束越强，高温产物气体自增强燃烧越迅速，装药反应越剧烈，壳体破坏时装药反应度越大；装药结构尺寸越大，炸药反应初期高温产物气体流动和表面燃烧导致裂纹增压扩展过程的时间越长，但后期反应越剧烈，壳体破坏时装药反应度越大；点火阈值压力对装药最终的反应烈度影响不明显。炸药燃烧裂纹网络反应演化模型可较好地反映炸药本征燃烧速率、约束强度、装药结构尺寸等对反应演化的影响规律，为弹药在意外刺激下的安全性设计和烈度量化评估提供了理论基础。

DUAN Z P , BAI Z L , BAI M J , et al . Burning-crack networks model for combustion reaction growth of solid explosives with strong confinement [J ] . Acta Armamentarii , 2021 , 42 ( 11 ): 2291 - 2299 . (in Chinese) DOI: 10.3969/j.issn.1000-1093.2021.11.001 http://doi.org/10.3969/j.issn.1000-1093.2021.11.001 A theoretical model for burning-crack networks is developed to characterize the non-shock initiation reaction growth behavior of solid explosives with strong confinement and give a quantification of reaction violence.The model is verified by comparing the calculated results with the experimental data. It is found that the stronger the confinement is，the faster the self-sustaining enhanced combustion is，and the more violent the reaction is for confinement failure. Moreover，the larger the charge size is，the longer the process of crack pressurization caused by gas flow and surface combustion at the initial reaction stage is，but the more violent the reaction is at the later self-sustaining enhanced combustion，and the greater the reaction degree is for confinement failure.The ignition intensity has no significant effect on the final reaction intensity of explosive charge.The results show that the theoretical burning-crack networks model is suitable for describing the effects of the intrinsic combustion rate of explosives，the confinement strength，the charge structure size，the air-gap volume and the pressure relief vent on the reaction growth of explosive charge，thus providing a theoretical method for the explosive safety design and the evaluation of explosives reaction violence.

MCCLELLAND M A , MAIENSCHEIN J L , NICHOLS A L , et al . ALE3D model predictions and materials characterization for the cookoff response of PBXN-109:UCRL-JC-145756 [R/OL ] . Livermore, CA , US : Lawrence Livermore National Lab. , 2002 .[2021-12-22 ] . https://www.osti.gov/biblio/15005681 https://www.osti.gov/biblio/15005681 https://www.osti.gov/biblio/15005681.

BERGHOUT H L , SON S F , SKIDMORE C B , et al . Combustion of damaged PBX 9501 explosive [J ] . Thermochimica Acta , 2002 , 384 ( 1 ): 261 - 277 . DOI: 10.1016/S0040-6031(01)00802-4 http://doi.org/10.1016/S0040-6031(01)00802-4 https://linkinghub.elsevier.com/retrieve/pii/S0040603101008024 https://linkinghub.elsevier.com/retrieve/pii/S0040603101008024

BERGHOUT H L , SON S F , HILL L G , et al . Flame spread through cracks of PBX 9501 (a composite octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine-based explosive) [J ] . Journal of Applied Physics , 2006 , 99 ( 11 ): 114901 . DOI: 10.1063/1.2196219 http://doi.org/10.1063/1.2196219 https://pubs.aip.org/jap/article/99/11/114901/143956/Flame-spread-through-cracks-of-PBX-9501-a https://pubs.aip.org/jap/article/99/11/114901/143956/Flame-spread-through-cracks-of-PBX-9501-a Recent experiments involving combustion of PBX 9501 [a plastic-bonded high explosive composed of 95% octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) by weight in a plasticized, estane-based binder] under confined conditions underscore the importance of cracks and flaws in reaction violence. The presence of a small void space or alternative escape path for combustion gases at the closed end of a crack drastically alters combustion violence. In the case of a true closed-ended crack, where gases can only escape by exiting the open end of the crack, luminous combustion spreads through the closed crack at relatively low rates in the range of a few meters per second, regardless of the pressure external to the slot. Hence, external pressure determines whether reaction can progress into the restricted dimensions of the slot, but it does not necessarily determine the dynamics of the flame’s progress in the slot. When an alternative combustion-gas escape path is available at the closed end of the slot, luminous combustion spreads through the crack at hundreds of meters per second. Additionally, combustion in cracks of confined PBX 9501 materials exhibits oscillatory behavior with a frequency of about 1000Hz for the experimental configuration used. This oscillatory behavior resembles combustion instabilities observed in rocket motors and may arise from similar processes. We also report on preliminary experiments involving 19.1cm long slots in confined PBX 9501, which have produced very high flame-propagation rates of 1500m∕s.

PARKER G R , HEATWOLE E M , HOLMES M D , et al . Deflagration-to-detonation transition in hot HMX and HMX-based polymer-bonded explosives [J ] . Combustion and Flame , 2020 , 215 : 295 - 308 . DOI: 10.1016/j.combustflame.2020.01.040 http://doi.org/10.1016/j.combustflame.2020.01.040 https://linkinghub.elsevier.com/retrieve/pii/S0010218020300523 https://linkinghub.elsevier.com/retrieve/pii/S0010218020300523

PARKER G R , DICKERSON P M , ASAY B W , et al . DDT of hot, thermally damaged PBX 9501 in heavy confinement:LA-UR-10-01356;LA-UR-10-1356 [R/OL ] . Los Alamos, NM , US : Los Alamos National Lab. (LANL), 2010 .[2021-10-12 ] . https://www.osti.gov/biblio/993109 https://www.osti.gov/biblio/993109 https://www.osti.gov/biblio/993109.

HOBBS M L , KANESHIGE M J . Cookoff of black powder and smokeless powder [J ] . Propellants, Explosives, Pyrotechnics , 2021 , 46 ( 3 ): 484 - 493 . DOI: 10.1002/prep.v46.3 http://doi.org/10.1002/prep.v46.3 https://onlinelibrary.wiley.com/toc/15214087/46/3 https://onlinelibrary.wiley.com/toc/15214087/46/3

GRAHAM K J . Mitigation of fuel fire threat to large rocket motors by venting [R/OL ] . Fort Belvoir, VA , US : Defense Technical Information Center , 2010 .[2022-05-26 ] . http://www.dtic.mil/docs/citations/ADA532243 http://www.dtic.mil/docs/citations/ADA532243 http://www.dtic.mil/docs/citations/ADA532243. DOI: 10.21236/ADA532243 https://dx.doi.org/10.21236/ADA532243 .

RICHARD T , WEIDHAAS J . Dissolution, sorption, and phytoremediation of IMX-101 explosive formulation constituents: 2,4-dinitroanisole(DNAN), 3-nitro-1,2,4-triazol-5-one(NTO),and nitroguanidine [J ] . Journal of Hazardous Materials , 2014 , 280 : 561 - 569 . DOI: 10.1016/j.jhazmat.2014.08.042 http://doi.org/10.1016/j.jhazmat.2014.08.042 https://linkinghub.elsevier.com/retrieve/pii/S0304389414007055 https://linkinghub.elsevier.com/retrieve/pii/S0304389414007055

MADEIRA C L , FIELD J A , SIMONICH M T , et al . Ecotoxicity of the insensitive munitions compound 3-nitro-1,2,4-triazol-5-one(NTO) and its reduced metabolite 3-amino-1,2,4-triazol-5-one (ATO) [J ] . Journal of Hazardous Materials , 2018 , 343 : 340 - 346 . DOI: 10.1016/j.jhazmat.2017.09.052 http://doi.org/10.1016/j.jhazmat.2017.09.052 https://linkinghub.elsevier.com/retrieve/pii/S0304389417307422 https://linkinghub.elsevier.com/retrieve/pii/S0304389417307422

TAPPAN B C , BOWDEN P R , LICHTHARDT J P , et al . Evaluation of the detonation performance of insensitive explosive formulations based on 3,3’ diamino-4,4’-azoxyfurazan (DAAF) and 3-nitro-1,2,4-triazol-5-one(NTO) [J ] . Journal of Energetic Materials , 2018 , 36 ( 2 ): 169 - 178 . DOI: 10.1080/07370652.2017.1334720 http://doi.org/10.1080/07370652.2017.1334720 https://www.tandfonline.com/doi/full/10.1080/07370652.2017.1334720 https://www.tandfonline.com/doi/full/10.1080/07370652.2017.1334720

DU L X S , JIN S H , SHU Q H , et al . The investigation of NTO/HMX-based plastic-bonded explosives and its safety performance [J ] . Defence Technology , 2022 , 18 ( 1 ): 72 - 80 . DOI: 10.1016/j.dt.2021.04.002 http://doi.org/10.1016/j.dt.2021.04.002 3-nitro-1,2,4-triazol-5-one (NTO) is the main component of insensitive munitions (IM) formulation because of its outstanding insensitive properties. In this paper, a series of NTO/HMX-based composite explosives were prepared and characterized. The study focuses on the effect of NTO on the performance of the formulations, especially the safety performance. The results revealed that the mechanical sensitivity of formulations was associated with NTO content, as well as the thermal conductivity, specific heat capacity and Arrhenius parameters. Then, the high amount of NTO using in formulation was proved to be helpful for NTO/HMX-based formulation to exhibit good thermal safety. Besides, by accelerating rate calorimeter (ARC) and a modified cook-off equipment, the pressure and pressure rise rate were proved as the important indicator for judging the thermal safety performance in confined spaces. Finally, the numerical simulation was used as a credible method for predicting the respond temperature of cook-off experiment. © 2021 China Ordnance Society

HENSON B F , SMILOWITZ L B . The chemical kinetics of solid thermal explosions [M/OL ] // ASAY B W. Shock Wave Science and Technology Reference Library, Vol. 5:Non-shock Initiation of Explosives.Berlin, Heidelberg,Germany:Springer , 2010 : 45 - 128 .[2021-11-13 ] . https://DOI.org/10.1007/978-3-540-87953-4_3 https://DOI.org/10.1007/978-3-540-87953-4_3 https:/ /DOI.org/10.1007/978-3-540-87953-4_3. DOI: 10.1007/978-3-540-87953-4_3 https://dx.doi.org/10.1007/978-3-540-87953-4_3 .

TERRONES G , SOUTO F J , BURKETT M W , et al . The effect of cook-off on the bulk permeability of a plastic bonded explosive [J ] . Propellants, Explosives,Pyrotechnics , 2006 , 31 ( 5 ): 333 - 342 . DOI: 10.1002/prep.v31:5 http://doi.org/10.1002/prep.v31:5 https://onlinelibrary.wiley.com/toc/15214087/31/5 https://onlinelibrary.wiley.com/toc/15214087/31/5

ASAY B W , SON S F , BDZIL J B . The role of gas permeation in convective burning [J ] . International Journal of Multiphase Flow , 1996 , 22 ( 5 ): 923 - 952 . DOI: 10.1016/0301-9322(96)00041-9 http://doi.org/10.1016/0301-9322(96)00041-9 https://linkinghub.elsevier.com/retrieve/pii/0301932296000419 https://linkinghub.elsevier.com/retrieve/pii/0301932296000419

XIONG W . A simole method for calculating detonation parameters of explosives [J ] . Journal of Energetic Materials , 1985 , 3 ( 4 ): 263 - 277 . DOI: 10.1080/07370658508012341 http://doi.org/10.1080/07370658508012341 http://www.tandfonline.com/doi/abs/10.1080/07370658508012341 http://www.tandfonline.com/doi/abs/10.1080/07370658508012341

叶青 , 余永刚 . 大尺寸固体火箭发动机快速烤燃特性的数值模拟 [J ] . 火炸药学报 , 2018 , 41 ( 6 ): 621 - 626 ,631. DOI: 10.14077/j.issn.1007-7812.2018.06.016 http://doi.org/10.14077/j.issn.1007-7812.2018.06.016 针对国内外火工品、炸药、发射药、推进剂增材制造技术,按照增材制造的技术特点和应用方向,综述了国内外增材制造技术在火炸药成型中的研究现状。概述了材料喷射成型(Material jetting)、材料挤出成型(Material extruding)、光聚合固化技术(Vat photopolymerization)的成型原理、工艺特点及在火炸药成型中的应用情况,介绍了各类增材制造技术中火炸药的物料特性,并对火炸药增材制造技术发展方向进行了预测。指出火炸药增材制造应按照火炸药的应用背景,对增材制造火炸药配方(即耗材)的能量特性、力学特性、能量释放特性及工艺适配性等进行系统研究,以满足不同应用背景的发展需求。附参考文献97篇。

YE Q , YU Y G . Numerical simulation of fast cook-off characteristics for a large scale solid rocket motor [J ] . Chinese Journal of Explosives & Propellants , 2018 , 41 ( 6 ): 621 - 626 ,631. (in Chinese)

SAHIN H , NARIN B , KURTULUS D F . Development of a design methodology against fast cook-off threat for insensitive munitions [J ] . Propellants, Explosives, Pyrotechnics , 2016 , 41 ( 3 ): 580 - 587 . DOI: 10.1002/prep.v41.3 http://doi.org/10.1002/prep.v41.3 https://onlinelibrary.wiley.com/toc/15214087/41/3 https://onlinelibrary.wiley.com/toc/15214087/41/3

戴湘晖 , 段建 , 沈子楷 , 等 . 侵彻弹体慢速烤燃响应特性实验研究 [J ] . 兵工学报 , 2020 , 41 ( 2 ): 291 - 297 . DOI: 10.3969/j.issn.1000-1093.2020.02.010 http://doi.org/10.3969/j.issn.1000-1093.2020.02.010 为考核全尺寸侵彻弹体的慢速烤燃响应特性，利用自行研制的慢速烤燃装置开展了实验。将质量为290 kg的侵彻弹体平放在慢烤箱中以3.3 ℃/h的升温速率缓慢加热，实时采集弹体表面温度曲线并拍摄整个实验过程，测量距弹体质心水平7 m处的反射冲击波峰值超压。实验结果表明：全尺寸侵彻弹体在加热42 h45 min23 s、温度达到约190 ℃时发生燃烧，41 s后发生了更为剧烈的反应，弹体和慢烤箱被炸裂成大块破片；通过反射冲击波超压峰值反推弹体剧烈反应时对应的等效裸露装药当量为4.153 kg，远小于实际装药当量和完全爆轰时的等效裸露装药当量；从加热时间、弹体表面温度、实验现场破坏情况、反射冲击波峰值超压、反应机理等方面综合判断该侵彻弹体的慢速烤燃响应类型为燃烧转爆炸。

DAI X H , DUAN J , SHEN Z K , et al . Experiment of slow cook-off response characteristics of penetrator [J ] . Acta Armamentarii , 2020 , 41 ( 2 ): 291 - 297 . (in Chinese) DOI: 10.3969/j.issn.1000-1093.2020.02.010 http://doi.org/10.3969/j.issn.1000-1093.2020.02.010 An experimental device was designed for evaluating the slow cook-off response characteristic of full-scale penetrator. The penetrator with a mass of 290 kg was placed in the slow cook-off oven and slowly heated at a heating rate of 3.3 ℃/h. The surface temperature of penetrator was collected in real time, and the whole experimental process was recorded. The peak value of reflected shock wave overpressure at a distance of 7 m from the mass center of penetrator was measured. The full-scale penetrator burns when it is heated for 42 hours, 45 minutes and 23 seconds and the temperature reaches 190 ℃, a more intense reaction occurs after 41 seconds, and the slow cook-off oven and the penetrator are exploded to form large fragments. The exposed explosive equivalent is deduced to be 4.153 kg from peak value of the reflected shock wave overpressure, which is far less than the actual charge equivalent and the exposed explosive equivalent during full detonation. Based on the analysis of the heating time, the surface temperature of penetrator, the damage on experimental site, the fragments of penetrator, the peak value of reflected shock wave overpressure and the reaction mechanism, the slow cook-off response type of penetrator is judged to be combustion-to-explosion transition.Key