The detection of low-energy deposition in the range of sub-eV through ionization using germanium (Ge) with a bandgap of
∼
0.7 eV requires internal amplification of the charge signal. This can be ...achieved through high electric field that accelerates charge carriers, which can then generate more charge carriers. The minimum electric field required to generate internal charge amplification is derived for different temperatures. We report the development of a planar point contact Ge detector in terms of its fabrication and the measurements of its leakage current and capacitance as a function of applied bias voltage. With the determination of the measured depletion voltage, the field distribution is calculated using GeFiCa, which predicts that the required electric field for internal charge amplification can be achieved in proximity to the point contact. The energy response to an Am-241 source is characterized and discussed. We conclude that such a detector with internal charge amplification can be used to search for low-mass dark matter.
For the first time, planar high-purity germanium detectors with thin amorphous germanium contacts were successfully operated directly in liquid nitrogen and liquid argon in a cryostat at the ...Max-Planck-Institut für Physics in Munich. The detectors were fabricated at the Lawrence Berkeley National Laboratory and the University of South Dakota, using crystals grown at the University of South Dakota. They survived long-distance transportation and multiple thermal cycles in both cryogenic liquids and showed reasonable leakage currents and spectroscopic performance. Also discussed are the pros and cons of using thin amorphous semiconductor materials as an alternative contact technology in large-scale germanium experiments searching for physics beyond the Standard Model.
•We address the optimal location of multiple types of BEV charging facilities, including dynamic wireless charging facilities and different levels of plug-in charging stations.•A tri-level ...programming is developed to model the presented problem.•An efficient solution algorithm is proposed to solve the model, wherein the formulated model is first treated as a black-box optimization, and then solved by an efficient surface response approximation model based solution algorithm.
To reduce greenhouse gas emissions in transportation sector, battery electric vehicle (BEV) is a better choice towards the ultimate goal of zero-emission. However, the shortened range, extended recharging time and insufficient charging facilities hinder the wide adoption of BEV. Recently, a wireless power transfer technology, which can provide dynamic recharging when vehicles are moving on roadway, has the potential to solve these problems. The dynamic recharging facilities, if widely applied on road network, can allow travelers to drive in unlimited range without stopping to recharge. This paper aims to study the complex charging facilities location problem, assuming the wireless charging is technologically mature and a new type of wireless recharging BEV is available to be selected by consumers in the future other than the traditional BEV requiring fixed and static charging stations. The objective is to assist the government planners on optimally locating multiple types of BEV recharging facilities to satisfy the need of different BEV types within a given budget to minimize the public social cost. Road users’ ownership choice among multiple types BEV and BEV drivers’ routing choice behavior are both explicitly considered. A tri-level programming is then developed to model the presented problem. The formulated model is first treated as a black-box optimization, and then solved by an efficient surface response approximation model based solution algorithm.
Abstract
Reconnection fronts, also known as dipolarization fronts (DFs), and kinetic Alfvén waves (KAWs) are two of the widely observed structures and waves in the terrestrial magnetotail, but their ...correlation remains elusive in previous spacecraft measurements. Using high-resolution Magnetospheric Multiscale data, here we provide the first observational identification of KAWs behind the DF. These low-frequency dispersive KAWs propagate quasi-perpendicular to the magnetic field at phase speeds slower than local Alfvén speed, and are highly correlated with high-frequency whistlers propagating obliquely to the magnetic field. Specifically, whistlers appear at local magnetic field minima (wave troughs of KAWs) and disappear at local magnetic field maxima (wave crests of KAWs), highly consistent with the source region of whistler waves previously reported near equator and dayside magnetopause. Our study also suggests that the KAWs behind DFs could originate from the diffusion region of magnetic reconnection. These findings improve our understanding of the relationship between DFs, KAWs, and whistler waves in terrestrial magnetotail.
With the development and application of advanced technologies such as Cyber Physical System, Internet of Things, Industrial Internet of Things, Artificial Intelligence, Big Data, Cloud Computing, ...Blockchain, etc., more manufacturing enterprises are transforming to intelligent enterprises. Smart manufacturing systems (SMSs) have become the focus of attention of some countries and manufacturing enterprises. At present, there are some applications of SMSs in different industrial fields. However, there is still a lack of a unified definition of SMSs and a unified analysis of requirements. In order to have a comprehensive understanding of SMSs, this paper summarized the evolution, definition, objectives, functional requirements, business requirements, technical requirements, and components of SMSs. At the same time, it points out the current development status and level. Based on above, an autonomous SMSs model driven by dynamic demand and key performance indicators is proposed. Through the review of this paper, the reference can be provided for the transformation of more manufacturing enterprises from the traditional to the intellectualized ones.
Elastic electron-proton scattering (e-p) and the spectroscopy of hydrogen atoms are the two methods traditionally used to determine the proton charge radius, r
. In 2010, a new method using muonic ...hydrogen atoms
found a substantial discrepancy compared with previous results
, which became known as the 'proton radius puzzle'. Despite experimental and theoretical efforts, the puzzle remains unresolved. In fact, there is a discrepancy between the two most recent spectroscopic measurements conducted on ordinary hydrogen
. Here we report on the proton charge radius experiment at Jefferson Laboratory (PRad), a high-precision e-p experiment that was established after the discrepancy was identified. We used a magnetic-spectrometer-free method along with a windowless hydrogen gas target, which overcame several limitations of previous e-p experiments and enabled measurements at very small forward-scattering angles. Our result, r
= 0.831 ± 0.007
± 0.012
femtometres, is smaller than the most recent high-precision e-p measurement
and 2.7 standard deviations smaller than the average of all e-p experimental results
. The smaller r
we have now measured supports the value found by two previous muonic hydrogen experiments
. In addition, our finding agrees with the revised value (announced in 2019) for the Rydberg constant
-one of the most accurately evaluated fundamental constants in physics.
In order to study the temporal and spatial variations of PM2.5 and its chemical compositions in the region of Beijing, Tianjin, and Hebei (BTH), PM2.5 samples were collected at four urban sites in ...Beijing (BJ), Tianjin (TJ), Shijiazhuang (SJZ), and Chengde (CD), and also one site at Shangdianzi (SDZ) regional background station over four seasons from 2009 to 2010. The samples were weighted for mass concentrations and analyzed in the laboratory for chemical profiles of 19 elements (Al, As, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Ni, P, Pb, Sr, Ti, V, and Zn), eight water-soluble inorganic ions (Na+ , NH4+ , K+ , Mg2+ , Ca2+ , Cl- , NO3- , and SO42- , and carbon fractions (OC and EC). The concentrations of PM2.5 and its major chemical species were season dependent and showed spatially similar characteristics in the plain area of BTH. The average annual concentrations of PM2.5 were 71.8-191.2 μg m-3 at the five sites, with more than 90% of sampling days exceeding 50 μg m-3 at BJ, TJ, and SJZ. PM2.5 pollution was most serious at SJZ, and the annual concentrations of PM2.5 , secondary inorganic ions, OC, EC, and most crustal elements were all highest. Due to stronger photochemical oxidation, the sum of concentrations of secondary inorganic ions (NH4+ , NO3- , and SO42- was highest in the summer at SDZ, BJ, TJ, and CD. Analysis of electric charges of water-soluble inorganic ions indicated the existence of nitric acid or hydrochloric acid in PM2.5 . For all five sites, the concentrations of OC, EC and also secondary organic carbon (SOC) in the spring and summer were lower than those in the autumn and winter. SOC had more percentages of increase than primary organic carbon (POC) during the winter. The sums of crustal elements (Al, Ca, Fe, Mg, Ti, Ba, and Sr) were higher in the spring and autumn owing to more days with blowing or floating dust. The concentrations of heavy metals were at higher levels in the BTH area by comparison with other studies. In Shijiazhuang and Chengde, the PM2.5 pollution was dominated by coal combustion. Motor vehicle exhausts and coal combustion emissions both played important roles in Tianjin PM2.5 pollution. However, motor vehicle exhausts had played a more important role in Beijing owing to the reduction of coal consumption and sharp increase of cars in recent years. At SDZ, regional transportation of air pollutants from southern urban areas was significant.
•The effects of thermal environment on human sleep was reviewed.•A thermal comfortable sleeping environment is important for sleep maintenance.•Air conditioner should be controlled to avoid decrease ...in air temperature toward morning.•Control of bed micro-environment may improve thermal comfort energy efficiently.
Thermal environment in bedrooms is still a largely neglected topic in thermal comfort research, although a thermal comfortable environment is important for sleep maintenance. Studies confirm that human body is sensitive to air temperature during sleep; even moderate heat or cold exposure decrease sleep quality significantly. In the present paper we reviewed air temperatures measured in bedroom and the effects of heat and cold exposure on sleep quality, and then proposed 5 aspects of approaches or technologies that could improve sleeping thermal environment at a low energy consumption. We concluded that there are two important research topics in sleeping thermal environment. One is to develop sleeping-mode control strategy for air conditioner used in bedroom to get slight increase or to avoid decrease in room air temperature when approaching morning. The other is to control bed micro-environment energy efficiently by using of local heating, cooling and/or ventilation system.
Knowledge of the impacts of climate change on agro-ecosystems is needed for developing optimal conservation and production practices. The objective of this study was to evaluate the potential impacts ...of projected climate changes during 2070–2099 under three emissions scenarios (A2a, and B2a, and GGa1) on hydrology, soil loss, and crop production in Changwu tableland region on southern Loess Plateau of China. Monthly projections for the periods of 1950–1999 and 2070–2099 were used from the Hadley Centre's general circulation model (HadCM3). A stochastic weather generator (CLIGEN) was used to downscale monthly HadCM3 projections to daily values at three spatial scales. The Water Erosion Prediction Project (WEPP) model was run for a wheat–wheat–maize rotation under conventional and conservation tillage at the 8.7% and 17.6% slopes. HadCM3 predicted a 23–37% increase in annual precipitation, 2.3–4.3
°C rise in maximum temperature, and 3.6–5.3
°C rise in minimum temperature for the region over the century. Compared with the present climate, predicted percent increases under climate changes, as averaged over the three spatial scales for each emissions scenario and slope, ranged from 29 to 79% for runoff, 2 to 81% for soil loss, 15 to 44% for wheat grain yield, 40 to 58% for maize yield, 25 to 28% for crop transpiration, 21 to 34% for soil evaporation, and 4 to 12% for long-term soil water reserve under the conventional tillage. However, adoption of the conservation (delayed) tillage could reduce runoff by 18–38%, and decrease soil loss by 56–68% as compared to the conventional tillage under the present climate. These results suggest that the use of the conservation tillage would be sufficient to maintain low runoff and erosion levels and thus protect agro-ecosystems under projected climate changes.
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