|
|
|
题名
|
作者
|
年代
|
出处
|
被引量
|
| 1 | Trends in Lipids Level and Dyslipidemia among Chinese Adults, 2002-2015显示文摘Objective To investigate the trends of lipid profiles and dyslipidemia among Chinese adults from 2002 to 2015.Methods Data were collected from three nationally representative cross-sectional surveys.Fasting venous blood samples were collected and serum lipids were tested by biochemical analysis and enzymatic determination.Lipid levels and the prevalence of dyslipidemia among adults were analyzed with complex sampling weighting adjustment for age and gender.Results The weighted means of TC, TG, and LDL-c significantly increased linearly from 3.93, 1.12, and 2.12 mmol/L in 2002 to 4.59, 1.41, and 2.78 mmol/L in 2010 and then to 4.63, 1.47, and 2.87 mmol/L in 2015, respectively;by contrast, HDL-c levels decreased significantly from 1.30 mmol/L to 1.26 mmol/L over the same period.Similar trends in mean non-HDL-c and lipid-related ratios were observed.The weighted dyslipidemia prevalence linearly increased;in particular, hypercholesterolemia increased from 1.6% to 5.6% and then to 5.8%, hypertriglyceridemia increased from 5.7% to 13.6% and then to 15.0%, low HDL-c increased from 18.8% to 35.5% and then to 24.9%, and high LDL-c increased from 1.3% to 5.6% and then to 7.2%(P for trend <0.001).Conclusion Dyslipidemia increased among Chinese adults from 2002 to 2015.Development of a comprehensive strategy to decrease lipid levels in this population is urgently required. | SONG Peng Kun MAN Qing Qing LI Hong PANG Shao Jie JIA Shan Shan LI Yu Qian HE Li ZHAO Wen Hua ZHANG Jian | 2019 | Biomedical and Environmental Sciences2019，32，8： | 45 |
| 2 | Malnutrition in Relation with Dietary, Geographical, and Socioeconomic Factors among Older Chinese显示文摘Objective Nutrition is closely related to the health of the elderly population. This study aimed to provide a comprehensive picture of the nutrition status of elderly Chinese and its related dietary,geographical, and socioeconomic factors.Methods A total of 13,987 ≥ 60-year-old persons from the 2010–2013 Chinese National Nutrition and Health Survey were included to evaluate various aspects of malnutrition, including underweight,overweight or obesity, and micronutrient inadequacy.Results Overall, the prevalence of obesity, overweight, and underweight was 12.4%, 34.8%, and 5.7%,respectively, with disparities both geographically and socioeconomically. The prevalence of underweight was higher among the older old(≥ 75 years), rural residents and those with low income, with low education status, and residing in undeveloped West areas. More than 75% of the elderly do not meet the Dietary Reference Intakes for vitamins A, B1, B2, and E, folate, calcium, selenium, potassium, biotin,and choline, with the prevalence of inadequate intake increasing with age for most nutrients. At the population level, the mean intakes of numerous food groups did not meet the recommendations by the Chinese Dietary Guideline.Conclusions Obesity epidemic, inadequacy of micronutrient intake, and high prevalence of underweight and anemia in susceptible older people are the major nutrition challenges for the rapidly aging population in China. | ZHANG Jian SONG Peng Kun ZHAO Li Yun SUN Ye YU Kai YIN Jing PANG Shao Jie LIU Zhen MAN Qing Qing HE Li LI Cheng ARIGONI Fabrizio BOSCO Nabil DING Gang Qiang ZHAO Wen Hua | 2021 | Biomedical and Environmental Sciences2021，34，5： | 5 |
| 3 | Low-cost and high-strength Mg-Al-Ca-Zn-Mn wrought alloy with balanced ductility显示文摘A novel low-cost Mg-Al-Ca-Zn-Mn-based alloy was developed to simultaneously improve its strength and ductility.The high yield strength of 411 MPa and the high elongation to failure of~8.9%have been achieved in the as-extruded Mg-1.3Al-1.2Ca-0.5Zn-0.6Mn(wt%)sample.Microstructure characterizations showed that the high strength is mainly associated with the ultra-fined dynamically recrystallized(DRXed)grains.Moreover,high-density dislocations in the un-DRXed region and nano-precipitates are distributed among theα-Mg matrix.The high ductility property can be ascribed to the high volume fraction of DRXed grains with a much randomized texture,as well as the formations of high-density subgrains in the un-DRXed grain regions. | Kun Yang Hucheng Pan Sen Du Man Li Jingren Li Hongbo Xie Qiuyan Huang Huajun Mo Gaowu Qin | 2022 | International Journal of Minerals,Metallurgy and Materials2022，29，7： | 3 |
| 4 | Projection of the Zhujiang(Pearl) River Delta's potential submerged area due to sea level rise during the 21st century based on CMIP5 simulations显示文摘Projections of potential submerged area due to sea level rise are helpful for improving understanding of the influence of ongoing global warming on coastal areas. The Ensemble Empirical Mode Decomposition method is used to adaptively decompose the sea level time series in order to extract the secular trend component. Then the linear relationship between the global mean sea level(GMSL) change and the Zhujiang(Pearl) River Delta(PRD)sea level change is calculated: an increase of 1.0 m in the GMSL corresponds to a 1.3 m(uncertainty interval from1.25 to 1.46 m) increase in the PRD. Based on this relationship and the GMSL rise projected by the Coupled Model Intercomparison Project Phase 5 under three greenhouse gas emission scenarios(representative concentration pathways, or RCPs, from low to high emission scenarios RCP2.6, RCP4.5, and RCP8.5), the PRD sea level is calculated and projected for the period 2006–2100. By around the year 2050, the PRD sea level will rise 0.29(0.21 to 0.40) m under RCP2.6, 0.31(0.22 to 0.42) m under RCP4.5, and 0.34(0.25 to 0.46) m under RCP8.5, respectively.By 2100, it will rise 0.59(0.36 to 0.88) m, 0.71(0.47 to 1.02) m, and 1.0(0.68 to 1.41) m, respectively. In addition,considering the extreme value of relative sea level due to land subsidence(i.e., 0.20 m) and that obtained from intermonthly variability(i.e., 0.33 m), the PRD sea level will rise 1.94 m by the year 2100 under the RCP8.5scenario with the upper uncertainty level(i.e., 1.41 m). Accordingly, the potential submerged area is 8.57×103 km2 for the PRD, about 1.3 times its present area. | XIA Jiangjiang YAN Zhongwei ZHOU Wen FONG Soi Kun LEONG Ka Cheng TANG Iu Man CHANG S W LEONG W K JIN Shaofei | 2015 | Acta Oceanologica Sinica2015，34，9： | 3 |
| 5 | Rhubarb-based Chinese herbal formulae for hepatic encephalopa-thy:a systematic review and Meta-analysis显示文摘OBJECTIVE: To evaluate the effectiveness and safety of rhubarb-based Chinese herbal formulae(RCHF), which are widely used to treat hepatic encephalopathy(HE) in China.METHODS: Nine online databases were searched from inception to November 22, 2016. Eligible studies were randomized controlled trials of Traditional Chinese Medicine(TCM) treatment for adult patients(≥ 18 years old) with HE. Outcomes such as mortality rate, clinical response rate, blood ammonia level, and alanine aminotransferase were evaluated between TCM group and control group.RESULTS: Thirty studies involving 2661 HE patients were analyzed. Most studies used RCHF treatment.Compared with conventional treatment as usual,lactulose, and vinegar, RCHF were associated with significant improvement in clinical response rate[risk ratio(RR) = 1.33, 95% confidence interval(CI) =1.25, 1.43, I2= 0%; RR = 1.26, 95% CI = 1.14, 1.38, I2=22%; and RR = 1.19, 95% CI = 1.06, 1.33, I2= 0%, respectively] and significant reductions in levels of blood ammonia and alanine aminotransferase. Only minor RCHF-associated adverse events, such as abdominal pain(0.3%), anal tenesmus(0.3%), and diarrhea(2.3%), were reported, and there were no significant differences in these events between the treatment group and the three types of control group.CONCLUSION: The findings suggest that RCHF may be an alternative treatment option for HE patients. More rigorous multicenter studies with larger samples and longer observational periods are needed to confirm these findings. | Zhang Ning Zhou Shuangnan Xiao Xiaohe Wanq Zhen Bai Yunfeng He Tingting Zhou Chao Wang Yao Kun Zhou Wang Zhongxia Liu Bing Larry J.Prokop Matthew C.Hernandez Li Jun Gong Man | 2017 | Journal of Traditional Chinese Medicine2017，37，6： | 3 |
| 6 | In-vitro biomineralization and biocompatibility of friction stir additively manufactured AZ31B magnesium alloy-hydroxyapatite composites显示文摘The present study aims to evaluate effect of hydroxyapatite(HA,Ca10(PO4)6OH2),a ceramic similar to natural bone,into AZ31B Mg alloy matrix on biomineralization and biocompatibility.The novel friction stir processing additive manufacturing route was employed to fabricate Mg-HA composites.Various HA contents(5,10,20 wt%)were incorporated into Mg matrix.Microstructural observation and chemical composition analysis revealed that refined Mg grains and dispersion of HA particles at micro/nanoscales were achieved in Mg-HA composites after the friction stir processing.The biomineralization evaluation were carried out using immersion experiments in simulated body fluid followed by mineral morphology observation and chemical composition analysis.The wettability measurements were conducted to correlate the biomineralization behavior.The results showed improvement in wettability and bone-like Ca/P ratio in apatite deposit on the composites compared to as-received Mg.In addition,the increase of blood compatibility,cell viability and spreading were found in the higher HA content composites,indicating the improved biocompatibility.Therefore,friction stir processed Mg-20 wt%HA composite exhibited the highest wettability and better cell adhesion among other composites due to the effect of increased HA content within Mg matrix. | Yee-Hsien Ho Kun Man Sameehan S.Joshi Mangesh V.Pantawane Tso-Chang Wu Yong Yang Narendra B.Dahotre | 2020 | Bioactive Materials2020，5，4： | 2 |
| 7 | Revolution of vitamin E production by starting from microbial fermented farnesene to isophytol显示文摘Vitamin E is one of the most widely used vitamins.In the classical commercial synthesis of vitamin E(a-tocopherol),the chemical synthesis of isophytol is the key technical barrier.Here,we establish a new process for isophytol synthesis from microbial fermented farnesene.To achieve an efficient pathway for farnesene production,Saccharomyces cerevisiae was selected as the host strain.First,b-farnesene synthase genes from different sources were screened,and through protein engineering and system metabolic engineering. | Ziling Ye Bin Shi Yanglei Huang Tian Ma Zilei Xiang Ben Hu Zhaolin Kuang Man Huang Xiaoying Lin Zhu Tian Zixin Deng Kun Shen Tiangang Liu | 2022 | The Innovation2022，3，3： | 2 |
| 8 | Three Dimensional Sulfur-doped Graphene Hydrogels with Tetrathiafulvalene for High Performance Supercapacitors显示文摘由把 tetrathiafulvalene 用作减少并且做代理人,三维(3D ) 做硫的 graphene hydrogels (SGH ) 轻易地在 dimethyl formamide 和水的混合溶剂被准备。几调查表明 TTF 在如此的唯一的 3D 体系结构的形成起一个关键作用,作为它不仅还原剂去进 3D 结构,而且罐头自己组装作为在减小进程做代理人被转变到 TTF ·+ 和 TTF 2+ 。同样准备的 SGH 的形态学,水晶结构,结合的化学药品,元素的作文和孔被学习了。得益于明确并且 cross-linked 3D 多孔的网络体系结构, supercapacitors 在 0.3 A·g −1 基于在 KOH 电解质的 SGH 展出了 212.5 F·g −1 的一个高特定的电容。而且,这个电容也证明好电气化学的稳定性和在骑车的重复控告 / 解除的可逆性的高度测试。 | Jingli Zhang Man Jiang Lingbao Xing Kun Qin Tianzhen Liu Jin Zhou Weijiang Si Hongyou Cui Shuping Zhuo | 2016 | Chinese Journal of Chemistry2016，34，1： | 2 |
| 9 | Pt nanocrystallines/TiO_2 with thickness-controlled carbon layers:Preparation and activities in CO oxidation显示文摘In this work, a series of Pt nanocrystallines(Pt NCs) supported on TiO_2 substrate with controlled thickness of carbon layers(C-Pt/TiO_2) were synthesized. Well-dispersed Pt NCs were facilely synthesized at room temperature by a photo-reduction process in lytropic liquid crystal(LCs). Surface tuning of the carbon layers on Pt/TiO_2 catalysts was achieved by varying the calcination atmospheres(in argon, air, and oxygen) and characterized by XPS and HRTEM. The influence of the coated carbon layers on the catalytic activity of catalysts is investigated by CO oxidation reaction which presented the following ranks: C-Pt/TiO_2-O_2> C-Pt/TiO_2-Air > C-Pt/TiO_2-Ar. It is found that the carbon layer coating can stabilize the Pt NCs and enable them anti-sintering at high temperature. This finding provides new insight into understanding the C-Pt/TiO_2 ternary system for tuning their catalytic performance. | Man Zhou Muhong Li Chujun Hou Zhongyu Li Yongzheng Wang Kun Xiang Xuefeng Guo | 2018 | Chinese Chemical Letters2018，29，6： | 2 |
| 10 | Community dynamics of ammonia oxidizing bacteria in a fullscale wastewater treatment system with nitrification stability显示文摘To determine whether the functional stability of nitrification was correlated to a stable community structure of ammonia oxidizing bacteria(AOB)in a fullscale wastewater treatment plant,the AOB community dynamics in a wastewater treatment system was monitored over one year.The community dynamics were investigated using specific PCR followed by terminal restriction fragment length polymorphism(T-RFLP)analysis of the amoA gene.The T-RFLP results indicated that during the period of nitrification stability,the AOB community structure in the full-scale wastewater treatment system was relatively stable,and the average change rate every 15 d of the system was 6.6%±5.8%.The phylogenetic analysis of the cloned amoA gene showed clearly that the dominant AOB in the system was Nitrosomonas spp.The results of this study indicated that throughout the study period,the AOB community structure was relatively stable in the full-scale wastewater treatment system with functional stability of nitrification. | Xiaohui WANG Xianghua WEN Hengjing YAN Kun DING Man HU | 2011 | Frontiers of Environmental Science & Engineering2011，5，1： | 2 |
| 11 | A Novel CoFe2NiMn0.3AlCux High-Entropy Alloy with Excellent Magnetic Properties and Good Mechanical Properties显示文摘In the present study,we investigate the crystal structure of high-entropy alloys(HEAs)in the form of CoFe2NiMn0.3AlCux(x=0.25,0.50,0.75,and 1.00)and their mechanical and magnetic properties.The CoFe2NiMn0.3AlCux alloys are composed of a mixture of a body-centered cubic(BCC)and a face-centered cubic(FCC)solid solution.The increased amounts of copper(Cu)boost both alloy strength and plastic ductility.The CoFe2 NiMn0.3AlCu1.0 HEAs demonstrate excellent mechanical properties,such as a high strength of 1832 MPa and a large plastic ductility of 22.38%.Magnetic property measurements on this alloy system indicated high saturated magnetization and high coercivity.The coercivity of the tested alloys lies in the range between 40 and 182 Oe,suggesting that the alloys have semi-hard magnetic properties.This study suggests that the present CoFe2NiMn0.3AlCux HEAs could serve as potential candidates for soft magnets in electromagnetic applications. | Man Zhu Chi Zhang Kun Li Yongqin Liu Mao Zhang Lijuan Yao Zengyun Jian | 2021 | Acta Metallurgica Sinica(English Letters)2021，34，11： | 1 |
| 12 | Direct numerical simulation of a near-field particle-laden plane turbulent jet显示文摘 | Jianren Fan Kun Luo Man Yeongha | 2004 | Physical Review E2004，70，2： | 1 |
| 13 | Direct synthesis of tin spheres/nitrogen-doped porous carbon composite by self-formed template method for enhanced lithium storage显示文摘To inhibit the agglomeration of tin-based nanomaterials and simplify the complicated synthesis process,a facile and eco-friendly self-formed template method is reported to synthesize tin submicron spheres dispersed in nitrogen-doped porous carbon(Sn/NPC)by pyrolysis of a mixture of disodium stannous citrate and urea.The vital point of this strategy is the formation of Na_(2)CO_(3)templates during pyrolysis.This self-formed Na_(2)CO_(3)acts as porous templates to support the formation of NPC.The obtained NPC provides good electronic conductivity,ample defects,and more active sites.Serving as anode for Li-ion batteries,the Sn/NPC electrode obtains a stable discharge capacity of 674.1 mAh/g after 150 cycles at 0.1 A/g.Especially,a high discharge capacity of 331.2 mAh/g can be achieved after 1100 cycles at 3 A/g.Additionally,a full cell coupled with LiCoO_(2)as cathode yields a discharge capacity of 524.8 mAh/g after 150 cycles at 0.1 A/g.In-situ XRD is implemented to investigate the alloying/dealloying reaction mechanisms.Density functional theory calculation ulteriorly explicates that NPC heightens intrinsic electronic conductivity,and NPC especially pyrrolic-N and pyridinic-N doping facilitates the Li-adsorption ability.Climbing image nudged elastic band method reveals low Li~+diffusion energy barrier in presence of N atoms,which accounts for the terrific electrochemical properties of Sn/NPC electrode. | Kun Liu Jia-ao Wang Hongfei Zheng Xiaodong Sun Zhimo Yang Jianzong Man Xinyu Wang Juncai Sun | 2022 | Journal of Materials Science & Technology2022，，9： | 1 |
| 14 | Penile replantation: report of two cases and review of the literature显示文摘阴茎切断和成功的种植园是很不平常的,为处理这个医药条件没有平淡的标准化过程。这里,我们报导包含导致不同致病的脉管的侮辱的不同的度的阴茎切断和种植园的二个案例临床的表示外科的途径和预后。这份报告用 bipedicled 描述了微外科的过程和手术后的照顾完成成功的嫁接并且工作的阴囊的拍动。 | LI Gui-zhong HE Feng HUANG Guang-ling MAN Li-bo LIU Kun SHEN Yu-ming | 2013 | Chinese Journal of Traumatology2013，16，1： | 1 |
| 15 | Achieving high strength above 400 MPa in conventionally extruded Mg-Ca-Zn ternary alloys显示文摘In this work,the role of Zn content in modifying the microstructure and mechanical properties of the Mg-1.2Ca-xZn(x=0.6,2.0 wt.%,named as XZ10-0 and ZX21-0,respectively)based alloys was studied,and it is found that the yield strength(YS)of the present Mg-(Zn)-Ca based alloys increases monotonically with increasing the Zn concentration,from~339 MPa in low-Zn content XZ10-0 sample to~406 MPa in high-Zn content ZX21-0 sample.Microstructure characterization shows that the enhanced YS can be attributed to the grain refinement,fine and dispersed nano-phases,a large number of lamellae structures,and the decrease of recrystallization fraction.TEM results show that the formation mechanism for the ultra-fine grains in present Mg-(Zn)-Ca based alloys can be attributed to the co-segregation of Ca and Zn elements at the grain boundary,as well as the dynamic nanoprecipitations.When the Zn content is high,the nano-phases in ZX21-0 sample belong to the Ca;Mg;Zn;ternary phases,which exert much higher thermal stability than the nano-sized Mg2 Ca binary phases formed in the low-Zn content XZ10-0 sample.The finer size and higher number density of the nano-Mg Zn Ca phases lead to the much finer grain size and sub-grain lamellae thickness in ZX21-0 sample,which thus results in the higher YS of~406 MPa. | DU Sen YANG Kun LI Man LI JingRen REN YuPing HUANG QiuYan PAN HuCheng QIN GaoWu | 2022 | Science China(Technological Sciences)2022，65，3： | 1 |
| 16 | Inhibition of cyclooxygenase/lipoxygenase from human platelets by polyhydroxylated/methoxylated flavonoids isolated from medicinal plants显示文摘 | Kun Man You Hyon-Gun Jong Hyun Pyo Kim | 1999 | Archives of Pharmacal Research1999，，1： | 1 |
| 17 | Theoreti- cal studies of high-nitrogen-containing energetic compounds based on the s-tetrazine Unit显示文摘 | MAN Tian-tian WANG Kun ZHANG Jian-guo | 2013 | Central European Journal Ener- getic Materials2013，10，： | 1 |
| 18 | Association between Baseline SBP/DBP and All-Cause Mortality in Residents of Shanxi,China:A Population-based Cohort Study from 2002 to 2015显示文摘Objective To investigate the association between blood pressure and all-cause mortality in Shanxi,China.Methods The‘2002 China Nutrition and Health Survey’baseline data in Shanxi province was used.A retrospective investigation was performed in 2015.The effects of SBP and DBP on the all-cause mortality were analyzed using the Cox regression model.The hazard ratio(HR)and 95%confidence interval(CI)were estimated by the sex and age groups.Results The follow-up rate was 76.52%over 13 years,while the cumulative mortality rate for all participants was 917.12/100,000 person-years.The mortality rose with an increasing SBP(χ_(trend)^(2)=270.537,P<0.001)or DBP level(χ_(trend)^(2)=57.240,P<0.001).After adjustment for the confounding factors,a significant association between mortality and high SBP(≥160 mm Hg)and high DBP(≥100 mm Hg),with adjusted HR ranging from 1.405-to 2.179-fold for SBP and 1.550-to 2.854-fold for DBP,was noted.Significant HRs for most DBP subgroups were found in>60-year-old participants.Males with DBP≥100 mm Hg had a significantly higher mortality,with an HR(95%CI)of 2.715(1.377–5.351).Conclusion Adults with SBP>160 mm Hg and DBP>100 mm Hg had a higher mortality risk.Sex and age difference was noted in both DBP and mortality risk. | WANG Zhuo Qun ZHAI Yi LI Man YANG Xiu Feng ZHANG Jian REN Ze Ping ZHANG Mei SONG Peng Kun ZHAO Yan Fang MI Sheng Quan ZHANG Lu YANG Mao Xiang ZHAO Wen Hua | 2021 | Biomedical and Environmental Sciences2021，34，1： | 0 |
| 19 | Diagnosis of Kaposi sarcoma by a modified fine needle aspiration method combing cell block in Chinese patients with human immunodeficiency virus/acquired immunodeficiency syndrome显示文摘To the Editor:Kaposi’s sarcoma(KS),a low-grade vascular tumor,is one of the most common neoplasms reported in patients with acquired immunodeficiency syndrome(AIDS).Based on epidemiological and clinical characteristics,four types of KS have been reported:classic KS,endemic KS(in equatorial Africa),AIDS-associated KS(AIDS-KS),and iatrogenic KS.Clinically,the presentation of KS can be variable with dark or brown macules,plaques,or nodules that may bleed or,ulcerate on the skin and mucous membranes.Besides,the lymph nodes and some visceral organs can also be involved in more advanced stages of the disease. | Lei Sun Liang Zhang Kun Yang Jia-Min Chen Xiang-Mei Chen Man Li Xin-Gang Zhou Zhi-Yuan Ma Li-Ming Qi Peng Wang | 2020 | Chinese Medical Journal2020，，23： | 0 |
| 20 | An effective strategy for dendrite free Li metal anodes:Nickel foam decorated with high lattice-matching CoN and CoF_(2) nanosheets for dense deposition显示文摘The notorious dendrite and infinite volume change seriously restrict the advancement of lithium metal anodes(LMAs),during the long-term process of stripping/plating.Herein,the nanosheets of metal fluoride(CoF_(2))and metal nitride(CoN)with magnificent lithiophilicity on the nickel(Ni)foam are designed as the“regulator”to uniform the Li plating and build stronger solid electrolyte interface(SEI)layer for dendrite free LMAs.The Ni foam offers abundant space to receive deposited Li metal.The CoN nanosheets can guarantee the fast transfer of electrons,which provides a stable interface of Li^(+)reduction.Moreover,the nanosheet structure with lithiophilicity would accelerate the move of Li+and decrease the nucleation barrier,due to the high lattice-matching of Li and CoN.Meanwhile,the CoF_(2) could increase the content of F(LiF)in the SEI layer,which enhances the strength and avoids the destruction of SEI layer.With the cooperation of CoN and CoF_(2),the composited anode(Li/NF@CNCF)exhibits ultra-long cycle performance(more than 1200 h)and fantastic structure stability at 1 mA·cm^(-2) with 1 mAh·cm^(-2).Based on the LiFePO_(4) and Li/NF@CNCF,the full cells deliver excellent specifical capacity and steady coulombic efficiency.The strategy contributes an effective approach to alleviate the issues of lithium metal anodes in the field of LMAs. | Wenlong Liu Jianzong Man Xiaodong Sun Ning Zhang Yehong Du Kun Liu Zhongsheng Wen Song Li Juncai Sun | 2024 | Nano Research2024，17，5： | 0 |
您所在的机构暂未开通此部分的功能，请联系管理员