The Cemented Material Dam： A New, Environmentally Friendly Type of Dam

The first author proposed the concept of the cemented material dam （CMD） in 2009. This concept was aimed at building an environmentally friendly dam in a safer and more economical way for both the dam and the area downstream. The concept covers the cemented sand, gravel, and rock dam （CSGRD）, the rockfill concrete （RFC） dam （or the cemented rockfill dam, CRD）, and the cemented soil dam （CSD）. This paper summarizes the concept and principles of the CMD based on studies and practices in projects around the world. It also introduces new developments in the CSGRD, CRD, and CSD.

CEPC Technical Design Report

The Circular Electron Positron Collider(CEPC)is a large scientific project initiated and hosted by China,fostered through extensive collaboration with international partners.The complex comprises four accelerators:a 30 GeV Linac,a 1.1 GeV Damping Ring,a Booster capable of achieving energies up to 180 GeV,and a Collider operating at varying energy modes(Z,W,H,and tt).The Linac and Damping Ring are situated on the surface,while the subterranean Booster and Collider are housed in a 100 km circumference underground tunnel,strategically accommodating future expansion with provisions for a potential Super Proton Proton Collider(SPPC).The CEPC primarily serves as a Higgs factory.In its baseline design with synchrotron radiation(SR)power of 30 MW per beam,it can achieve a luminosity of 5×10^(34)cm^(-2)s^(-1)per interaction point(IP),resulting in an integrated luminosity of 13 ab^(-1)for two IPs over a decade,producing 2.6 million Higgs bosons.Increasing the SR power to 50 MW per beam expands the CEPC's capability to generate 4.3 million Higgs bosons,facilitating precise measurements of Higgs coupling at sub-percent levels,exceeding the precision expected from the HL-LHC by an order of magnitude.This Technical Design Report(TDR)follows the Preliminary Conceptual Design Report(Pre-CDR,2015)and the Conceptual Design Report(CDR,2018),comprehensively detailing the machine's layout,performance metrics,physical design and analysis,technical systems design,R&D and prototyping efforts,and associated civil engineering aspects.Additionally,it includes a cost estimate and a preliminary construction timeline,establishing a framework for forthcoming engineering design phase and site selection procedures.Construction is anticipated to begin around 2027-2028,pending government approval,with an estimated duration of 8 years.The commencement of experiments and data collection could potentially be initiated in the mid-2030s.

Review of drought impacts on carbon cycling in grassland ecosystems

Grasslands play a key role in both carbon and water cycles.In semi-arid and arid grassland areas,the frequency and intensity of droughts are increasing.However,the influence of a drought on grassland carbon cycling is still unclear.In this paper,the relationship between drought and grassland carbon cycling is described from the perspective of drought intensity,frequency,duration,and timing.Based on a large amount of literature,we determined that drought is one of the most prominent threats to grassland carbon cycling,although the impacts of different drought conditions are uncertain.The effects of a drought on grassland carbon cycling are more or less altered by drought-induced disturbances,whether individually or in combination.Additionally,a new conceptual model is proposed to better explain the mechanism of droughts on grassland carbon cycling.At present,evaluations of the effects of droughts on grassland carbon cycling are mainly qualitative.A data fusion model is indispensable for evaluating the fate of carbon cycling in a sustainable grassland system facing global change.In the future,multi-source data and models,based on the development of single and multiple disturbance experiments at the ecosystem level,can be utilized to systematically evaluate drought impacts on grassland carbon cycling at different timescales.Furthermore,more advanced models should be developed to address extreme drought events and their consequences on energy,water,and carbon cycling.

Several issues to be considered for long-term better behavior of concrete gravity dams

Along with economic,social quick development and urbanization,dams and reservoirs are of strategic importance for flood control,water supply,electricity production,irrigation,etc.,both for developed countries and for developing countries.Climate change is a new challenging issue to be considered which will speed up the development of hydropower in developing countries.More and more attention will be paid on the long-term better behavior of dams to guarantee the safety of the people involved and the better development of the world.There are about 50000 old dams in the world and a lot of them have been completed and operated for more than 50 years.However,how do we evaluate the dams’safety?How do we make the decision to do rehabilitation work or to rebuild a new dam based on evaluation results?The life span and the real safety status of old dams becomes a challenging task for the dam society,especially for China because it has more than 6000 dams to be evaluated and rehabilitated within the next few years.Based on the investigation of the Fengman gravity dam,which is 91.7 m high,operated since 1943 and suffered uplift pressure,freeze and thaw problems,etc.,discussions on the life span evaluation of old concrete gravity dams have been made.The reasonable coefficient of dam safety has been discussed.The social decision for the final choice after comprehensive studies has been introduced.