k-center问题的算法研究综述

k-center问题是设施选址的基础问题,同样是NP难问题,在分配、紧急服务等领域也有着实际的应用。随着问题规模的扩大,原有的算法已不再适用,需要进一步优化或者改进。为了找到求解该问题的高效算法,对现有算法进行研究。对各类求解k-center问题的算法进行梳理,将求解算法划分为精确算法、启发式算法、元启发式算法、近似算法等,从算法原理、改进思路、性能和精度等方面进行对比综述。精确算法在求解小规模k-center问题时可在多项式时间内得到最优解,但是算法效率低,不适用于大规模问题;启发式算法可以在多项式时间内给出相对最优解,但是没有理论保证,无法衡量与最优解的关系;元启发式算法可对目前存在的智能优化算法进行改进,给出相对最优解,但是解的质量无法保证;利用近似算法得到的解具有近似比保证,有较大的理论研究价值,但是实用价值较弱。目前求解k-center问题的元启发式算法已取得一定的研究成果,但是在求解时间、求解规模、算法效率等方面仍待突破,这将是未来k-center问题的研究重点。

Comprehensive epidemiological assessment of trauma incidents at a level I trauma center

BACKGROUND The continuous development of social and economic progress and ongoing enhancement of infrastructure construction has led to drastic changes in the occurrence of trauma.AIM To analyze the epidemiological characteristics of trauma in Lanzhou City to provide theoretical references for improving quality of trauma care.METHODS A retrospective analysis of clinical data from 16585 trauma patients treated at the First Hospital of Lanzhou University Trauma Center from November 1,2021 to October 31,2023 was conducted.Data including age,sex,time of trauma,cause of trauma,and major injured body parts were statistically analyzed.RESULTS A total of 18235 patients were admitted,with complete data for 16585 cases.Of these,9793 were male and 6792 were female(male-to-female ratio of 1.44:1).The peak times for trauma occurrence were 10 AM-12 PM and 6-10 PM,and the peak months were from May to October.The leading causes of trauma were falls(45.32%),other trauma(15.88%),road traffic accidents(15.15%),violence(10.82%),cutting/stabbing(9.41%),mechanical injuries(2.65%),winter sports injuries(0.36%),animal bites(0.22%),burns(0.09%),and electrical injuries(0.02%).The distribution of majorly injured body parts showed statistical significance,with limbs/skin being the most affected followed by the head/neck,chest/abdomen,and back.CONCLUSION Medical institutions and government agencies can implement preventive measures and policies based on the characteristics of trauma determined in this study to enhance the quality and level of trauma care.

基于k-center聚类和最近邻中心的公平数据汇总

公平数据汇总是指从每种数据类别中选择有代表性的子集,且满足公平性要求。在大数据时代,每种类别的数据都是海量的,因此公平数据汇总研究具有非常重要的现实意义。为了使公平数据汇总的数据点更具有代表性,提出了基于k-center聚类和最近邻中心的公平数据汇总算法。算法主要包括2个基本步骤:(1)通过k-center聚类,将k个簇中心作为当前汇总结果;(2)选择满足公平约束的原簇中心的最近邻点作为新簇中心。由于更新簇中心时选择的是原簇中心的最近邻点,因此相对随机选择的数据点,最近邻点更具有代表性,是除原始簇中心外的次优代表点。同时,寻找最近邻点作为新的簇中心能最大限度减少公平代价。在2个模拟数据集和6个UCI真实数据集上的对比实验结果表明,所提出的算法在近似因子和公平代价方面都优于对比算法,说明所提出的算法获得的数据汇总更具有代表性。

A nanosecond level current pulse capture taper optical fiber probe based on micron level nitrogen-vacancy color center diamond

This work demonstrates a micron-sized nanosecond current pulse probe using a quantum diamond magnetometer.A micron-sized diamond crystal affixed to a fiber tip is integrated on the end of a conical waveguide.We demonstrate real-time visualization of a single 100 nanosecond pulse and discrimination of two pulse trains of different frequencies with a coplanar waveguide and a home-made PCB circuit.This technique finds promising applications in the display of electronic stream and can be used as a pulse discriminator to simultaneously receive and demodulate multiple pulse frequencies.This method of detecting pulse current is expected to provide further detailed analysis of the internal working state of the chip.

Cortical hem signaling center: functions, development, and potential implications for evolution and brain disorders

Development of the telencephalon relies upon several signaling centers-localized cellular populations that supply secreted factors to pattern the cortical neuroepithelium.One such signaling center is the cortical hem,which arises during embryonic development at the telencephalic dorsal midline,adjacent to the choroid plexus and hippocampal primordium(Figure 1A).While the cortical hem has also been described in reptiles and birds,most of our knowledge about the developmental roles of the cortical hem is derived from the analysis in mice.The cortical hem produces several types of secreted molecules,including wingless-related integration site(Wnt)and bone morphogenetic(Bmp)proteins.The cortical hem is particularly important for the development of the hippocampus,which is involved in learning and memory,and the neocortex,which is the most complex brain region that mediates multiple types of behavior and higher cognitive functions(Mangale et al.,2008;Dal-Valle-Anton and Borrell,2022).

Comparison of different severity scores in correlating hemoglobin levels with the severity of hepatic decompensation: An observational study

BACKGROUND Chronic liver disease is a growing global health problem,leading to hepatic decompensation characterized by an array of clinical and biochemical complic-ations.Several scoring systems have been introduced in assessing the severity of hepatic decompensation with the most frequent ones are Child-Pugh score,model of end-stage liver disease(MELD)score,and MELD-Na score.Anemia is frequently observed in cirrhotic patients and is linked to worsened clinical outcomes.Although studies have explored anemia in liver disease,few have investigated the correlation of hemoglobin level with the severity of hepatic decompensation.AIM To determine the relationship between hemoglobin levels and the severity of decompensated liver disease and comparing the strength of this correlation using the Child-Pugh,MELD,and MELD-Na scores.METHODS This cross-sectional study was conducted at a tertiary care hospital with 652 decompensated liver disease patients enrolled in the study.Data was collected on demographics,clinical history,and laboratory findings,including hemoglobin levels,bilirubin,albumin,prothrombin time(international normalized ratio),sodium,and creatinine.The Child-Pugh,MELD,and MELD-Na scores were calculated.Statistical analysis was performed using Statistical Package for the Social Sciences version 26,and correlations between hemoglobin levels and severity scores were assessed using Spearman's correlation coefficient.RESULTS The study included 405 males(62.1%)and 247 females(37.9%)with an average age of 58.8 years.Significant inverse correlations were found between hemoglobin levels and Child-Pugh,MELD,and MELD-Na scores(P<0.01),with the MELD scoring system being the strongest correlator among all.One-way analysis of variance revealed significant differences in hemoglobin levels across the severity groups of each scoring system(P=0.001).Tukey's post hoc analysis confirmed significant internal differences among each severity group.CONCLUSION Understanding the correlation between hemoglobin and liver disease severity can improve patient management by offering insights into prognosis and guiding treatment decisions.

Comprehensive Level One Trauma Center Could Lower In-hospital Mortality of Severe Trauma in China

Trauma is a major health and social problem in the US and China, It constitutes the main cause of death in people aged 45 or under in both countries112]. There is clear evidence from clinical studies that a large percentage of these deaths are needless and preventable if better treatment and prevention programs are available12-3].

Correlation between Geographical Regional Economy and Construction of County-level Vocational Education Centers

In the period of Eleventh Five-Year Plan,the construction of county-level vocational education centers in Shanxi Province made great contribution to local social and economic development. Due to influence of special geography,population environment and regional economic development situation,it forms the pattern of strong in southeast and weak in northwest. Thus,scientific making plan for construction of vocational education centers in northwestern counties( cities) and establishing long-term mechanism for construction of vocational education centers will be helpful for serving regional economic construction.

Syntheses of molecular wires containing redox center:Reversible redox property and good energy level matching with Au electrode

Molecular wires with tetrathiafulvalene （TTF） as redox center were synthesized and characterized. UV-vis spectra and cyclic voltammetry showed these wires had good reversible redox behavior under ambient conditions and their HOMO energy levels （--5.0 eV） matched well with the Fermi level of Au （--5.1 eV）.

Practical Experience of Establishing German Standard Level 1 Perinatal Center in Chongqing Health Care for Women and Children

Germany,as a western developed country,has an advanced medical level,especially in the health care of very immature premature infants.We trace the medical history of perinatology to understand the development of perinatal centers in Germany.After analyzing the classification and function,hierarchical management and quality control systems of German perinatal centers,we established a German standard level 1 perinatal center in the Chongqing Health Center for Women and Children(CHCWC).During more than two years of practice,we changed concepts,continuously updated clinical knowledge and skills,developed a series o f high-quality work processes and supervision systems and introduced advanced medical equipment.We believe that the experience of establishing a German standard level 1 perinatal center and perinatal center network in Chongqing is worthy of being promoted to the Chinese maternal and child health care system.

SOPA:Source Routing Based Packet-Level Multi-Path Routing in Data Center Networks

Many ＂rich - connected＂ topologies with multiple parallel paths between smwers have been proposed for data center networks recently to provide high bisection bandwidth, but it re mains challenging to fully utilize the high network capacity by appropriate multi- path routing algorithms. As flow-level path splitting may lead to trafl＇ic imbalance between paths due to flow- size difference, packet-level path splitting attracts more attention lately, which spreads packets from flows into multiple available paths and significantly improves link utilizations. However, it may cause packet reordering, confusing the TCP congestion control algorithm and lowering the throughput of flows. In this paper, we design a novel packetlevel multi-path routing scheme called SOPA, which leverag- es OpenFlow to perform packet-level path splitting in a round- robin fashion, and hence significantly mitigates the packet reordering problem and improves the network throughput. Moreover, SOPA leverages the topological feature of data center networks to encode a very small number of switches along the path into the packet header, resulting in very light overhead. Compared with random packet spraying （RPS）, Hedera and equal-cost multi-path routing （ECMP）, our simulations demonstrate that SOPA achieves 29.87%, 50.41% and 77.74% higher network throughput respectively under permutation workload, and reduces average data transfer completion time by 53.65%, 343.31% and 348.25% respectively under production workload.

Cumulative effects of excess high-normal alanine aminotransferase levels in relation to new-onset metabolic dysfunction-associated fatty liver disease in China

BACKGROUND Within the normal range,elevated alanine aminotransferase(ALT)levels are associated with an increased risk of metabolic dysfunction-associated fatty liver disease(MAFLD).AIM To investigate the associations between repeated high-normal ALT measurements and the risk of new-onset MAFLD prospectively.METHODS A cohort of 3553 participants followed for four consecutive health examinations over 4 years was selected.The incidence rate,cumulative times,and equally and unequally weighted cumulative effects of excess high-normal ALT levels(ehALT)were measured.Cox proportional hazards regression was used to analyse the association between the cumulative effects of ehALT and the risk of new-onset MAFLD.RESULTS A total of 83.13%of participants with MAFLD had normal ALT levels.The incidence rate of MAFLD showed a linear increasing trend in the cumulative ehALT group.Compared with those in the low-normal ALT group,the multivariate adjusted hazard ratios of the equally and unequally weighted cumulative effects of ehALT were 1.651[95%confidence interval(CI):1.199-2.273]and 1.535(95%CI:1.119-2.106)in the third quartile and 1.616(95%CI:1.162-2.246)and 1.580(95%CI:1.155-2.162)in the fourth quartile,respectively.CONCLUSION Most participants with MAFLD had normal ALT levels.Long-term high-normal ALT levels were associated with a cumulative increased risk of new-onset MAFLD.

Place of Otorhinolaryngological (ENT) Diseases in a 2<i>nd</i>Level Health Center: Case of the of Commune V (CSRéf CV) Reference Health Center of the District of Bamako

Objective: Provide the place of ENT diseases at the Reference Health Center of the Commune V of Bamako. Materials and Method: A cross-sectional study using ENT medical assessment was carried out from January 2017 to December 2017 at the Reference Health Center of Commune V of Bamako’s District. Results: 1911 patients were included and that number represented 15.46% of all non-obstetrics medical consultations in the health center. The sex ratio was 0.83 for women (54.7%). The average age was 22 years old. Otologic diseases were 66.4% of the cases followed by nasal sinus cases (16.6%). Infectious and inflammatory diseases were 74.1% and were the main diagnosed diseases. The difficulties were mainly from technical platform. Conclusion: The diversity of these pathologies required a strong development or reinforcement of human and material resources capacities in of these structures for proximity care management.

The Level of Knowledge, Behaviors, and Attitudes on Rational Use of Drugs of Patients Who Applied to the Family Health Center in Istanbul, Türkiye: A Cross-Sectional Study

Background: This study, it was aimed to determine the level of knowledge, attitudes, and behaviors of patients who applied to a family health center about the rational use of drugs. Irrational use of drugs is a major problem worldwide. WHO reports that half of the patients do not use their drugs correctly. Methods: This cross-sectional study was conducted between 1 October 2017 and 30 November 2018 at Istanbul Fatih Family Health Center No 7. The sample size was determined as 301 people selected by systematic sampling method from patients aged 18 and older. Results: The mean age of the participants was 53.8% ± 16.8%, 59.8% were female, 62.5% were married, and 52.5% were primary school graduates. 63.9% of the participants knew the names of the drugs they used, and 79.9% of them knew the indication for use. 89% of individuals check the expiry date of the drugs before using them, and 83.1% read the drug prospectus. 84% of the participants support the prohibition of using over-the-counter drugs. Conclusion: The level of knowledge of the participants about the rational use of drugs is above the societal average. However, some issues need more awareness. The high level of rational use of drugs awareness of physicians and pharmacists will also strengthen the rational use of drugs and indirectly increase the awareness of the public.

Investigate Stressors Levels and Identify Coping Strategies of Frontline Nurses during the COVID-19 in Sharjah Primary Health Center—A Quantitative Research Study

During the COVID-19 Epidemic, nurses are usually informed of emotional exhaustion, increased workloads, and uncertainty, leading to burnout. Consequently, psychological health initiatives are essential to support nurses during a pandemic. This project aims to investigate the stress levels and identify the Coping Strategies of Nurses during the COVID-19 Epidemic in Sharjah Primary Health Center, as they are always at the front line of this epidemic. The nature of their work, they are mainly infected and spread the virus amongst colleagues and family. The target population is nurses working in Sharjah primary health centers, and the number sample is 230. The researcher sent the survey through the link. And in this research, we used two instruments which include the Expanded Nursing Stress Scale and The Coping Strategies Scale (CSS). This study shows that the most stressful factor is related to workload, especially related to unpredictable staffing and scheduling. On the other hand, the most coping strategies were those that were associated with Meaning-focused Coping Strategies, especially believing that valuable lessons can learn from undesirable experiences.

Activating d^(10)electronic configuration to regulate p-band centers as efficient active sites for solar energy conversion into H_(2)by surface atomic arrangement

Relationship between the activity for photocatalytic H_(2)O overall splitting(HOS)and the electron occupancy on d orbits of the active component in photocatalysts shows volcanic diagram,and specially the d^(10)electronic configuration in valley bottom exhibits inert activity,which seriously fetters the development of catalytic materials with great potentials.Herein,In d^(10)electronic configuration of In_(2)O_(3)was activated by phosphorus atoms replacing its lattice oxygen to regulate the collocation of the ascended In 5p-band(Inɛ5p)and descended O 2p-band(Oɛ2p)centers as efficient active sites for chemisorption to*OH and*H during forward HOS,respectively,along with a declined In 4d-band center(Inɛ4d)to inhibit its backward reaction.A stable STH efficiency of 2.23%under AM 1.5 G irradiation at 65°C has been obtained over the activated d^(10)electronic configuration with a lowered activation energy for H_(2)evolution,verified by femtosecond transient absorption spectroscopy,in situ diffuse reflectance infrared Fourier transform spectroscopy and theoretical calculations of dynamics.These findings devote to activating d^(10)electronic configuration for resolving the reaction energy barrier and dynamical bottleneck of forward HOS,which expands the exploration of high-efficiency catalytic materials.

Uniform isochronous center of a class of higher degree polynomial differential systems

In this paper,we give the necessary and sufficient conditions for a class of higher degree polynomial systems to have a uniform isochronous center.At the same time,we prove that for this system the composition conjecture is correct.

A high-efficiency transformer-in-package isolated DC-DC converter using glass-based fan-out wafer-level packaging

A transformer-in-package(TiP)isolated direct current-direct current(DC-DC)converter using glass-based fan-out wafer-level packaging(FOWLP)is proposed.By using 3-layer redistribution layers(RDLs),both the transformer and interconnections are built without an additional transformer chip,and the converter only has 2 dies:a transmitter(TX)chip and a receiver(RX)chip.The proposed solution results in a significant reduction in the cost and makes major improvements in the form factor and power density.Moreover,the transformer built by the RDLs achieves a high quality factor(Q)and high coupling factor(k),and the efficiency of the converter is thus improved.The TX and RX chips were implemented in a 0.18μm Biopolar CMOS DMOS(BCD)process and embedded in a compact package with a size of 5 mm×5 mm.With an output capacitance of 10μF,the converter achieves a peak efficiency of 46.5%at 0.3 W output power and a maximum delivery power of 1.25 W,achieving a maximum power density of 50 mW/mm2.

Water, Sanitation and Hygiene in Lower-Level Health Care Facilities of Dar es Salaam Region in Tanzania: Status towards Achieving the Sustainable Development Goals and Way Forward

Background: Improving Water, Sanitation and Hygiene in health care settings is a critical prerequisite for achieving national health goals and Sustainable Development Goals (SDGs). The World Health Organization (WHO) has set a target for each United Nations member state to reach by 2030. Each member state is required to reach by 2022, 2025 and 2030 at least 60%, 80% and 100%, respectively of basic level of service of the five elements which are water, sanitation, hygiene, waste management and environmental cleaning. Methods: This study aimed to evaluate and document the current state of basic water, sanitation, and hygiene services in all lower-level health care facilities in the Dar es Salaam region of Tanzania as of July 2022. A cross-sectional study was conducted in 99 public dispensaries in the Dar es Salaam region’s five councils: Ubungo, Kigamboni, Kinondoni and Temeke Municipalities, and Ilala City. The interviewee form and observational checklists were both digitalized using the Kobo tool software. The respondents were health care facility in-charges or nurse in-charges. Data were downloaded, validated, and imported to Stata version 15 for analysis. Results: The basic WASH level per JMP is far below the target in 2022. Each member state by 2022 is required to reach at least 60% of the basic level of service of each element. We found a low coverage of basic WASH in the 99 dispensaries included in this study. The basic WASH coverage was met in only 10 (10.1%) of the dispensaries, while the remaining 89 (89.9%) dispensaries fall on limited WASH services. Conclusion: This study revealed lower coverage of basic WASH services in dispensaries. An urgent need is required to improve the status of WASH in all the dispensaries and facilitate the provision of quality health care services, patient safety and reduce health care associated infections.

Preparing highly entangled states of nanodiamond rotation and NV center spin

A nanodiamond with an embedded nitrogen-vacancy(NV)center is one of the experimental systems that can be coherently manipulated within current technologies.Entanglement between NV center electron spin and mechanical rotation of the nanodiamond plays a fundamental role in building a quantum network connecting these microscopic and mesoscopic degrees of motions.Here we present a protocol to asymptotically prepare a highly entangled state of the total quantum angular momentum and electron spin by adiabatically boosting the external magnetic field.