Distinguishing f(R) theories from general relativity by gravitational lensing effect

The post-Newtonian formulation of a general class of f(R) theories is set up to 3rd order approximation. It turns out that the information of a specific form of f(R) gravity is encoded in the Yukawa potential, which is contained in the perturbative expansion of the metric components. Although the Yukawa potential is canceled in the 2nd order expression of the effective refraction index of light, detailed analysis shows that the difference of the lensing effect between the f(R) gravity and general relativity does appear at the 3rd order when $\sqrt{f''(0)/f'(0)}$ is larger than the distance $d_0$ to the gravitational source. However, the difference between these two kinds of theories will disappear in the axially symmetric spacetime region. Therefore only in very rare case the f(R) theories are distinguishable from general relativity by gravitational lensing effect at the 3rd order post-Newtonian approximation.Comment: 14 page

Connection Dynamics of Reduced 5-dimensional Kaluza-Klein Theory and Its Deparametrization

The connection dynamics of the 5-dimensional Kaluza-Klein theory reduced on 4-dimensional spacetime is obtained by performing the Hamiltonian analysis and canonical transformations. Deparametrization is achieved in the spherically symmetric model of the theory without introducing additional matter fields beyond the 5-dimensional gravity. Thus the physical time evolution and the physical spatial coordinate can be provided by the geometrical degrees of freedom in the higher dimensional spacetime

Aboveground net primary productivity of vegetation along a climate-related gradient in a Eurasian temperate grassland: spatiotemporal patterns and their relationships with climate factors

Accurate assessments of spatiotemporal patterns in net primary productivity and their links to climate are important to obtain a deeper understanding of the function, stability and sustainability of grassland ecosystems. We combined a satellite-derived NDVI time-series dataset and field-based samples to investigate spatiotemporal patterns in aboveground net primary productivity (ANPP), and we examined the effect of growing season air temperate (GST) and precipitation (GSP) on these patterns along a climaterelated gradient in an eastern Eurasian grassland. Our results indicated that the ANPP fluctuated with no significant trend during 2001-2012. The spatial distribution of ANPP was heterogeneous and decreased from northeast to southwest. The interannual changes in ANPP were mainly controlled by year-to-year GSP; a strong correlation of interannual variability between ANPP and GSP was observed. Similarly, GSP strongly influenced spatial variations in ANPP, and the slopes of fitted linear functions of the GSP-ANPP relationship increased from arid temperate desert grassland to humid meadow grassland. An exponential function could be used to fit the GSP-ANPP relationship for the entire region. An improved moisture index that combines the effects of GST and GSP better explained the variations in ANPP compared with GSP alone. In comparisons with the previous studies, we found that the relationships between spatiotemporal variations in ANPP and climate factors were probably scale dependent. We imply that the quantity and spatial range of analyzed samples contribute to these different results. Multi-scale studies are necessary to improve our knowledge of the response of grassland ANPP to climate change.ArticleENVIRONMENTAL EARTH SCIENCES.76(1):56(2017)journal articl

Highly controllable and reliable ultra-thin Parylene deposition

Thanks to the excellent barrier property and fabrication accessibility, Parylene has been actively used in the microelectromechanical system. An ultra-thin Parylene film with thickness smaller than 100 nm is usually required to precisely tune the surface property of substrate or protect the functional unit. The commercially available regular Parylene deposition is a dimer mass determined chemical vapor deposition process with a high output (i.e. a low deposition precision in term of thickness control), around 1.6 μm/g (the ratio of film thickness to the loaded dimer mass) for the machine in the author’s lab. Therefore, it is hard to controllably and reliably prepare a Parylene film with thickness smaller than 100 nm, which requires a dimer mass less than 62.5 mg. This paper reported a method to prepare ultra-thin Parylene films with the nominal thickness down to 1 nm. A home-made deposition chamber was put inside and connected with the regular machine chamber through a microfabricated orifice with feature size smaller than 1 mm. According to the free molecular flow theory, the pressure inside the deposition chamber can be predictably and controllably reduced, thereby an ultra-low output of Parylene deposition, as low as 0.08 nm/g, was successfully obtained. The deposition precision was increased by 4 orders of magnitude compared to that of a direct Parylene deposition. This highly controllable and reliable ultra-thin Parylene deposition technique will find promising applications in flexible electronics and biomedical microdevices

The Yuan-Tseh Lee Array for Microwave Background Anisotropy

The Yuan-Tseh Lee Array for Microwave Background Anisotropy (AMiBA) is the first interferometer dedicated to studying the cosmic microwave background (CMB) radiation at 3mm wavelength. The choice of 3mm was made to minimize the contributions from foreground synchrotron radiation and Galactic dust emission. The initial configuration of seven 0.6m telescopes mounted on a 6-m hexapod platform was dedicated in October 2006 on Mauna Loa, Hawaii. Scientific operations began with the detection of a number of clusters of galaxies via the thermal Sunyaev-Zel'dovich effect. We compare our data with Subaru weak lensing data in order to study the structure of dark matter. We also compare our data with X-ray data in order to derive the Hubble constant.Comment: accepted for publication in ApJ (13 pages, 7 figures); a version with high resolution figures available at http://www.asiaa.sinica.edu.tw/~keiichi/upfiles/AMiBA7/pho_highreso.pd

Field study of indoor environment quality in an open atrium with ETFE membrane in a healthcare facility

The hospital street is widely utilized in the modern health care facilities as a main traffic streamline to connecting all of the outpatient rooms and treatment departments for easy access. This study investigate the indoor environment quality of a typical hospital street, i.e., a high space atrium with ETFE membrane structure in the top. The investigation combines the on-site measurement and subjective survey. The results indicates that the indoor air temperature in the atrium reaches up to 32.6oC in a summer day causing thermal discomfort according to ASHRAE 55. The CO2, PM2.5, TVOC concentration in the hospital street comply with the Chinese standard for hospitals. The illumination in the corridors around the atrium is below the threshold of Chinese standard, i.e., 100 lux. Due to the vibration of the light ETFE membrane structure, the noise level in rainy days is as high as 79.5 dB which causes acoustic discomfort of occupants. This study is beneficial for the design of the hospital street design with the ETFE membrane structure