经济周期的测定对宏观经济政策的制定与实施具有重要意义。本文详细介绍了美国国民经济研究局的两种非参数周期测算方法:NBER方法、BB及BBQ方法。探讨并对比了Stock and Watson总结并提出的先加总后测定与先测定后加总这两类拐点识别方...经济周期的测定对宏观经济政策的制定与实施具有重要意义。本文详细介绍了美国国民经济研究局的两种非参数周期测算方法:NBER方法、BB及BBQ方法。探讨并对比了Stock and Watson总结并提出的先加总后测定与先测定后加总这两类拐点识别方法的原理,并分别用两种方法对美国1959年-2010年的经济周期拐点进行测算,实证得出先测定后加总方法在大数据前提下优于前者。本文通过对经济周期测定方法和拐点识别方法的研究,以期为我国测定经济周期和建立年表提供理论参考。展开更多
For the release of hazardous contaminant indoors, source identification is critical for developing effective response measures. A method which can quickly and accurately identify the position, emission rate, and relea...For the release of hazardous contaminant indoors, source identification is critical for developing effective response measures. A method which can quickly and accurately identify the position, emission rate, and release time of a single constant contaminant source by using real sensors was presented. The method was numerically demonstrated and validated by a case study of contaminant release in a three-dimensional office. The effects of the measurement errors and total sampling period of sensor on the performance of source identification were thoroughly studied. The results indicate that the adverse effects of the measurement errors can be mitigated by extending the total sampling period. For reaching a desirable accuracy of source identification, the total sampling period should exceed a certain threshold, which can be determined by repeatedly running the identification method tmtil the results tend to be stable. The method presented can contribute to develop an onsite source identification system for protecting occupants from indoor releases.展开更多
This paper study stability of saturated salt solutions cells at 25 ℃. These cells were prepared and measured at National Institute for Standard （NIS-Egypt） to study the stability of the saturated salt solutions. Th...This paper study stability of saturated salt solutions cells at 25 ℃. These cells were prepared and measured at National Institute for Standard （NIS-Egypt） to study the stability of the saturated salt solutions. The study was carried out using three saturated salt solutions, which are Potassium Acetate 22.5%, Potassium Iodide 68.9% and Potassium Sulphate 97.3% to cover low, medium and high relative humidity. The study was carried out using different shapes and volumes half liter spherical, liter spherical and liter conical per each salt which was prepared. The apparatus which used in measurement system in the first time are the same which used after ten years. The results show that the change of relative humidity value after ten years ranged from 0.1% to 0.7%. This value is suitable within uncertainty ＋ 2%. The period of stability for each run for all cells was found to be more than five hours and this period enough for calibration. The measurements show that the cells are stable for more than ten years with accepted value.展开更多
For the test of rotation speed of high spinning projectile, the general formula of the motional electromotive force （MEMF） of planar magnetic induction coil （PMIC） is derived in case of 3D rotation in a stable mag...For the test of rotation speed of high spinning projectile, the general formula of the motional electromotive force （MEMF） of planar magnetic induction coil （PMIC） is derived in case of 3D rotation in a stable magnetic field. Under a reasona-ble assumption, the MEMF of PMIC is simplified after the aforementioned general formula is used to calculate high spinning PMIC in the geomagnetic field environment. The determination approach of half-cycle is discussed and the method of rotation speed test is studied, and a test is conducted in the paper. The rotation speed curve obtained by the approach in this paper is consistent with the curve by telemetry.展开更多
The observation of friction anisotropy on graphene by friction measurement at atomic scale has been reported in this paper.Atomic-scale friction measurement revealed friction anisotropy with a periodicity of 60°,...The observation of friction anisotropy on graphene by friction measurement at atomic scale has been reported in this paper.Atomic-scale friction measurement revealed friction anisotropy with a periodicity of 60°,which is consistent with the hexagonal periodicity of the graphene.Both experiments and theory show that the value of the friction force is related to the graphene lattice orientation,and the friction force along armchair orientation is also larger than the one along zigzag orientation.These results will play a critical role in the use of graphene to manufacture nanoscale devices.展开更多
文摘经济周期的测定对宏观经济政策的制定与实施具有重要意义。本文详细介绍了美国国民经济研究局的两种非参数周期测算方法:NBER方法、BB及BBQ方法。探讨并对比了Stock and Watson总结并提出的先加总后测定与先测定后加总这两类拐点识别方法的原理,并分别用两种方法对美国1959年-2010年的经济周期拐点进行测算,实证得出先测定后加总方法在大数据前提下优于前者。本文通过对经济周期测定方法和拐点识别方法的研究,以期为我国测定经济周期和建立年表提供理论参考。
基金Project(50908128) supported by the National Natural Science Foundation of ChinaProject(51125030) supported by the National Science Foundation for Distinguished Young Scholars in China
文摘For the release of hazardous contaminant indoors, source identification is critical for developing effective response measures. A method which can quickly and accurately identify the position, emission rate, and release time of a single constant contaminant source by using real sensors was presented. The method was numerically demonstrated and validated by a case study of contaminant release in a three-dimensional office. The effects of the measurement errors and total sampling period of sensor on the performance of source identification were thoroughly studied. The results indicate that the adverse effects of the measurement errors can be mitigated by extending the total sampling period. For reaching a desirable accuracy of source identification, the total sampling period should exceed a certain threshold, which can be determined by repeatedly running the identification method tmtil the results tend to be stable. The method presented can contribute to develop an onsite source identification system for protecting occupants from indoor releases.
文摘This paper study stability of saturated salt solutions cells at 25 ℃. These cells were prepared and measured at National Institute for Standard （NIS-Egypt） to study the stability of the saturated salt solutions. The study was carried out using three saturated salt solutions, which are Potassium Acetate 22.5%, Potassium Iodide 68.9% and Potassium Sulphate 97.3% to cover low, medium and high relative humidity. The study was carried out using different shapes and volumes half liter spherical, liter spherical and liter conical per each salt which was prepared. The apparatus which used in measurement system in the first time are the same which used after ten years. The results show that the change of relative humidity value after ten years ranged from 0.1% to 0.7%. This value is suitable within uncertainty ＋ 2%. The period of stability for each run for all cells was found to be more than five hours and this period enough for calibration. The measurements show that the cells are stable for more than ten years with accepted value.
基金National Key Lab for Electronic Measurement and Technology,North University of China(No.9140C120401080C12)
文摘For the test of rotation speed of high spinning projectile, the general formula of the motional electromotive force （MEMF） of planar magnetic induction coil （PMIC） is derived in case of 3D rotation in a stable magnetic field. Under a reasona-ble assumption, the MEMF of PMIC is simplified after the aforementioned general formula is used to calculate high spinning PMIC in the geomagnetic field environment. The determination approach of half-cycle is discussed and the method of rotation speed test is studied, and a test is conducted in the paper. The rotation speed curve obtained by the approach in this paper is consistent with the curve by telemetry.
基金supported by the National High Technology Research and Development Program of China(Grant No.2009AA03Z316)the National Natural Science Foundation of China(Grant Nos.60904095,51050110445 and 61175103)the CAS FEA International Partnership Program for Creative Research Teams
文摘The observation of friction anisotropy on graphene by friction measurement at atomic scale has been reported in this paper.Atomic-scale friction measurement revealed friction anisotropy with a periodicity of 60°,which is consistent with the hexagonal periodicity of the graphene.Both experiments and theory show that the value of the friction force is related to the graphene lattice orientation,and the friction force along armchair orientation is also larger than the one along zigzag orientation.These results will play a critical role in the use of graphene to manufacture nanoscale devices.
