Lessons Africa Can Learn From China’s Experience in Urbanization

The rapid urbanization of Africa is facing a multitude of challenges.This paper analyzes the seven major issues currently plaguing African urbanization:regional development imbalances,the disconnect between urbanization and economic growth,increasing complexities in the urbanization process,the constraining effect of lagging agriculture,low quality of urbanization,lack of coordination between urbanization and modernization,and excessive population concentration in urban areas.To address these issues,Africa can draw valuable lessons from other countries,particularly from China’s experience in urban development.Since 1978,China has seen a rapid increase in its urbanization rate.The key to this success lies in policy orientation,labor force transition,prioritized regional development,and attracting foreign investment among other strategies.By learning from China’s experience,African countries can optimize agricultural modernization,strengthen the manufacturing sector,increase investment in infrastructure,and accelerate the process of digitization,thereby creating new opportunities for their urbanization process.This paper explores the rapidly developing urbanization process in Africa and the accompanying challenges.It also analyzes China’s experience in urbanization,offering insights and recommendations for Africa’s urban development.

Urbanization,unemployment rate and China' rising divorce rate

This paper analyzes the impacts of urbanization and unemployment rate on China's divorce rate with the panel data of 31Chinese provinces from 2000 to 2011.The study manifests as follows.First,the significant influence of urbanization cannot be observed on the rising breakdown since the latter is not the inevitable result of the former.In the second place,unemployment rate has a significant negative influence on divorce rate,namely,with the former increasing,the latter will decrease,which echoes the perspective of divorce cost.And finally,this paper also finds positive effects of per capita fixed investment,old-age dependency rate,average household size,the proportion of floating population and population density,and negative correlation of average education attainment on divorce rate.

Urban Expansion in Major Grain Producing Area from 1978 to 2017:A Case Study of Zhengzhou Metropolitan Area,China

The spatial form of urbanization in China has developed from single-core city expansion to a multi-center metropolitan area.However,little attention has been paid to the growth process of the emerging metropolitan area situated in major grain producing locations in the central China.Taking the Zhengzhou metropolitan area(ZZMA)as a case study,we developed an inverse S-shape model to characterize the spatial distribution of urban land density,and constructed an urban expansion core index,urban expansion intensity index,and urban compactness index to quantify the spatial structure change that has taken place from 1978 to 2017 during the process of urban expansion.Moreover,cropland contribution rate(CR)was constructed to evaluate the impacts of urban expansion on croplands.We uncovered four key findings.First,over the past 40 yr,the ZZMA has experienced dramatic expansion,and the central city of Zhengzhou expanded faster than other cities.The gravity centers of urban expansion of surrounding cities were moving toward to Zhengzhou City.Second,the urban land density decreased with the distance from the city center to the outskirts.As the only large city,Zhengzhou has experienced the fastest and most compact centralized urban expansion,especially after 2000,while other medium-and small-sized cities have experienced low-intensity decentralized expansion.Third,the urban core has been gradually expanding outward.From 1978 to 2017,the hot-zone of urban growth has moved progressively with the acceleration of urbanization.All cities except Jiaozuo had a single peak in different periods.Forth,the cities in national core grain-producing areas has higher cropland contribution rates and lower urban expansion areas,which was closely related to cropland protection.Further analysis showed that large city was relatively better positioned than smaller cities in the efficiency of their urban infrastructure and the effectiveness of wealth creation efficiency in the urbanized area could be tested in all cities,and the policy factor seemed to play an important role in the urban expansion process.

Carrier rate of hepatitis B surface antigen (HBsAg) among urban pregnant women in a secondary health facility in Maiduguri, Northeastern Nigeria

A serological survey conducted among 196 pregnant women resident in and around Maiduguri, an urban town in north eastern Nigeria showed that 33 (16.8%) were asymptomatic carriers of hepatitis B virus surface antigen (HBsAg). They are within the age range of 14-40 years with mean (± SD) age of 24.7 (± 6.3). The women attend antenatal clinic at the State Specialist Hospital, a secondary health facility in Maiduguri, Borno state. The women are all heterosexuals. The distribution of HBsAg carrier rate according to age of women studied showed a significant (p = 0.0061) increase of the prevalence of HBsAg from 4 (8.7%) in the lower age group (39 years). According to the number of pregnancies, the prevalence of HBsAg infection increased significantly from 6 (9.2%) among primiparous to 13 (13.7%) and 14 (38.9%) among multiparous and grand multiparous respectively. The carrier rate of HBsAg infection among the pregnant women studied based on their duration of pregnancies and their social class showed no significant differences. However, according to the factors known to be commonly associated with the highest risk of transmission of HBV such as history of blood transfusion, Tribal marks/tattooing, use of sharps, sharing of articles, history of jaundice in the women and husbands, history of sexually transmitted infections (STIs) of the women and husbands and the type of marriage (monogamous or polygamous), number of sexual relationships per week, only the history of blood transfusion was significantly associated with HBsAg carrier rate (RR = 3.71., 95% Confidence Interval (C.I.), 1.89-7.30, p = 0.0078). The study confirms that pregnant women who attend antenatal clinic in this secondary health facility are at higher risk of being infected with the HBV, which could lead to both prenatal and post natal transmission to their newborns.

Influence of RMB exchange rate fluctuation on urban-rural income from the perspective of transmission asymmetry

Based on time series data of RMB exchange rate and urban-rural income, this paper makes an empirical study for the influence of RMB exchange rate fluctuation on urban-rural income by utilizing rolling regression model through direct and indirect transmission mechanisms. According to the results, the transmission effect of RMB exchange rate fluctuation on urban-rural income has features of incompleteness and asymmetry. Moreover, RMB appreciation will help to reduce the urban-rural income gap. Therefore, this paper suggests that the Chinese economy should accelerate the course of transforming mode, adjusting structure and promoting development under the new normal. Meanwhile, reform of RMB exchange rate mechanism should be promoted, living standard of residents must be improved, and the urban-rural income gap should be reduced.

Effects of urban street trees on human thermal comfort and physiological indices: a case study in Changchun city, China

Planting trees along urban streets is one of the most important strategies to improve the urban thermal environment.However,the net impacts of urban street trees on human thermal comfort and physiological parameters are still less clear.On three similar east-west orientated streets with different degrees of tree cover-low(13%),medium(35%),and high(75%),urban microclimatic parameters and human physiological indices for six male students were simultaneously measured on three cloudless days in summer 2018.The results show that the differences in tree cover were predominant in influencing urban thermal environment and comfort.The street with the highest tree cover had significantly lower physiological equivalent temperature(PET) and more comfortable than the other two streets.The frequency of strong heat stress(PET> 35℃) was 64%,11 %,and 0%,respectively,for streets with low,medium,and high tree cover.For the six male university students,human physiological indices varied greatly across the three streets with different tree cover.Systolic blood pressure,diastolic blood pressure,and pulse rate increased with decreasing tree cover.The results also suggest that urban thermal environment and comfort had considerable impact on human physiological parameters.Our study provides reasons for urban planners to plant trees along streets to improve the thermal environment and promote urban sustainability.

A Kinetic Study of Anaerobic Biodegradation of Food and Fruit Residues during Biogas Generation Using Initial Rate Method

A kinetic study of biogas production from Urban Solid Waste (USW) generated in Dar es Salaam city (Tanzania) is presented. An experimental bioreactor simulating mesophilic conditions of most USW landfills was developed. The goal of the study was to generate the kinetic order of reaction with respect to biodegradable organic waste and use it to model biogas production from food residues mixed with fruit waste. Anaerobic biodegradation was employed under temperature range of 28℃ - 38℃. The main controls were leachate recirculation and pH adjustments to minimize acid inhibitory effects and accelerate waste biodegradation. The experimental setup comprised of three sets of bioreactors. A biodegradation rate law in differential form was proposed and the numerical values of kinetic order and rate constant were determined using initial rate method as 0.994 and 0.3093 mol0.006·day-1, respectively. Results obtained were consistent with that found in literature and model predictions were in reasonable agreement with experimental data.

Discussion on the Operation of Urban Domestic Sewage Treatment Facilities: A Case Study of Guangdong Province

Urban sewage treatment facility is an important ways to control polluted domestic water. The operation of urban sewage treatment facilities is good or not, and whether the effectiveness of pollutant emission reduction can be exerted play a significant role in reducing the pollution of living sources. Nowadays the operation of urban sewage treatment facilities is mainly evaluated by the load rate. However, due to the failure to fully implement the reformation of the rainwater and polluted water in Guangdong Province, the domestic sewage is mixed with rainwater during the rainy season and is included in the treatment of urban sewage treatment facilities. Therefore, it is not objective to evaluate the operation of sewage treatment facilities using only the load rate of sewage treatment. According to the situation of Guangdong Province, the load rates of COD, ammonia nitrogen and total phosphorus in domestic sewage and load rate of sewage treatment were included in the evaluation, and 20 urban sewage treatment facilities were selected as research objects. The operation situations and emission reduction benefits of urban sewage treatment facilities in different regions of Guangdong Province were roughly evaluated.

Analysis of Urban Heat Island Effect Using an Improved CTTC and STTC Model

An improved cluster thermal time constant(CTTC) and surface thermal time constant(STTC) numerical model was introduced,which took into account the effect of vegetation coverage and modified the expression of net longwave radiation of the canyon layer.In the case study the model was used to calculate the air temperature variation at downtown of Tianjin City.The relative error between the calculated and measured air temperatures was less than 3%.The tendency of air temperature variation was predicted when the building aspect ratio,vegetation rate,and wind speed changed respectively.It is demonstrated that when the aspect ratio of a building with south-north orientation increased,the heat island intensity at day time was mitigated;however,it became worse after sunset.The vegetation coverage rate and wind speed both had negative relationship with the urban heat island intensity.

Natural radioactive environment of urban soils in Shihezi, China

Radionuclides, such as 238U, 232Th and 40K, can be found in urban soil. To evaluate the natural radioactivity in the environment, soil samples were collected form Shihezi city and radioisotope concentrations were determined by X-ray fluorescence. The dose rate of urban soil (mGy per year, mGy/a) was calculated. The results indicate that the U, Th and K concentrations of the urban soils were, respectively, 1.2-3.2 mg/kg, 6.4-12.3 mg/kg and 2.05%-2.24%, with the mean values of 2.47 mg/kg, 10.47 mg/kg and 2.16 %. Dose rates of urban soils were 10.04-19.55 mGy/a with the mean value of 16.31 mGy/a. This dose rate is the perfect and maximum value of natural radiation in soil and different with the air absorbed dose rate from terrestrial γ-rays. The mean value of air absorbed dose rate was about 57.42 nGy/h. The annual effective dose rate in air was about 0.07 mSv/a and the average value of Raeq in urban soil was 120.37 Bq/kg. The relative contribution of α particle to the dose rate is higher than that derived from β- and γ-rays in the urban soils.

GM(1,1)模型在安徽省城镇化水平预测中的应用

为了推进安徽省城镇化建设,制定正确的城镇发展方针政策是十分必要的.而对安徽省未来城镇化水平进行合理预测则可为政府制定城镇发展方针政策提供理论依据.现选取2010~2021年的安徽省城镇化率作为研究数据,采用GM(1,1)模型对安徽省城镇化水平建立动态预测模型,并对建立的模型进行了检验.研究表明:GM(1,1)模型具有较好的拟合精度,建模精度达到99.38%.运用GM(1,1)模型对2022~2026年安徽省城镇化率进行预测,预测结果显示未来几年安徽省城镇化水平将呈上升趋势.

城市绿地乔木固碳能力及碳抵消效果评估

定量测算城市绿地乔木固碳能力及抵消碳排放,可为森林城市建设的树种选择和配置提供决策支持。基于高清卫星遥感影像数据和有关经济社会统计数据,结合实地调查,利用生物量模型法测算南充市主城区绿地乔木的固碳能力,探讨群落结构与固碳能力的影响;分析抵消城市能源CO_(2)排放的成效。结果表明:1)南充市主城区绿化植被中木本植物共269种,分属76科163属。出现频度最高的为桂花、银杏、黄葛树、天竺桂、樟木、樱花等10个树种。2)各类绿地林分平均密度677±425株·hm^(-2),平均胸径21.01±7.15 cm,平均树高8.52±2.06 m。3)各类绿地碳密度按大小为广场用地>附属绿地>公园绿地>防护绿地;固碳速率最大的是附属绿地(2.54 t·hm^(-2)·a^(-1)),最小的是公园绿地(1.64 t·hm^(-2)·a^(-1))。4)南充市主城区绿地乔木2020年碳固定量为9 347 t,能源CO_(2)总排放量为1 016.55万t,绿地乔木大约抵消城市能源0.09%CO_(2)的排放量。最后,建议南充市在城市森林营建过程中,应优先考虑多树种混合使用,并适时调整群落密度以优化林分结构、改善生境条件,促进林木整体水平的生长,进而提高群落的固碳能力;同时尽量采用近自然、较为粗放的经营方式,以减少碳排放。

整合多因素影响的城市消防站布局优化实践

为了科学规划城市消防站的数量和空间位置,提高同等时间下对责任区域的覆盖率,保证应急救援的时效性,避免可能导致的更大程度人员伤亡和财产损失,本研究以《城市消防站建设标准》为依据,运用地理信息系统(GIS),增加危险化学品重点单位的权重,根据调研情况提出10 min内90%覆盖率为考量标准,充分考虑保留现有消防站同时建设新站的经济成本和不合理布局对消防救援人员健康造成的危害,进行城市消防站布局优化。据此思路,以包头市昆区为例开展实践研究,结果表明:昆区消防站布局优化后,在相同阻抗中断下,消防站可达区域面积和对责任区域覆盖率均有较大增长。因此,运用该思路开展城市消防站布局优化具有一定的科学性。

农村成长经历会影响城镇家庭储蓄率吗?——来自CHFS 2019的经验证据

由于城市与农村的经济金融环境存在显著差异,成年前在农村成长的城镇居民比在城市成长的城镇居民具有较高的风险厌恶程度和较低的金融知识水平,从而更加偏向低消费和高储蓄。采用中国家庭金融调查(CHFS)2019年数据,将“目前居住在城市地区且拥有非农业户口、18岁之前为农业户口”作为“拥有农村成长经历”的界定标准,实证检验城镇家庭户主的农村成长经历对其家庭储蓄率的影响,结果表明:户主拥有农村成长经历的城镇家庭比户主没有农村成长经历的城镇家庭有更高的储蓄率,风险态度和金融素养在其中发挥了中介作用,即拥有农村成长经历的户主会因较高的风险厌恶程度和较低的金融知识水平而导致其家庭储蓄率较高;农村成长经历对储蓄率的正向影响在户主受教育水平较高、家庭资产较少、经济发展水平较低地区(中西部地区)的家庭中更为显著。因此,需要从改善城市的经济金融状况(降低生活成本、增强社会保障、减少不确定性等)入手来释放城镇居民的消费需求,并通过改善风险态度、加强金融教育、缩小城乡差距等渠道来降低农村成长经历对城镇家庭储蓄率的正向影响。

智能网联车专用道内队列控制模型

在智能网联车与人工驾驶车辆混合通行的场景中,为提高混行交通流的通行效率,提出了一种智能网联车专用道内车辆按编队行驶的队列控制模型。根据快速路道路条件和智能网联车的运行模式,通过分析智能网联车专用道内前后两车的运动过程,构建了智能网联车车队创建、加入和巡航控制模型,并求解出专用道内智能网联车形成编队行驶的最优策略。为验证队列控制模型的有效性,利用SUMO仿真平台搭建单车道和多车道仿真场景,模拟智能网联车在专用道内形成车队的过程,统计分析车流的通行效率,其中单车道仿真结果显示,相比于传统CACC跟驰模型,队列控制模型能将车辆编队时间减少23.06%;多车道仿真结果显示,当CAV渗透率在23.22%~40%时,队列控制模型下的车辆平均行程时间缩短17%。这表明在智能网联车专用道内,队列控制模型能更有效地利用专用道的空间资源,从而缩短车辆编队时间,提高智能网联环境下混行交通流的通行效率,故可用于混行交通流下智能网联车专用道的设置。

Impact of Local Climate Zones on the Urban Heat and Dry Islands in Beijing:Spatial Heterogeneity and Relative Contributions

Based on the building height and density data on a 100-m resolution,hourly 2-m temperature and humidity data at83 automatic weather stations,and gridded local climate zone(LCZ)data on a 120-m resolution in urban Beijing in2020,this study first employs the semivariogram combined with building parameters to calculate spatial correlations and has identified an LCZ grid resolution of 500 m suitable for best usage of the available observation data.Then,how the spatially heterogeneous LCZs affect and contribute to the canopy urban heat island intensity(UHII)and urban dry island intensity(UDII)are quantitatively investigated.It is found that UHII is high in winter and low in summer with a unimodal diurnal variation while UDI is low in winter but high in summer with a bimodal diurnal variation.The LCZ with compact mid-rise(open high-rise)buildings exhibits the highest UHII(UDII),followed by the compact high-rise(compact low-rise),while the LCZ of scattered trees presents both the lowest UHII and the lowest UDII.The most significant difference in the UHII(UDII)among the nine LCZ types in the urban area of Beijing is2.62℃(1.1 g kg^(-1)).Area-weighted averaging analysis reveals that the open mid-rise LCZ is the most significant contributor to the UHII(UDII),immediately followed by compact mid-rise(open low-rise),with the least contribution from bare rock or paved(scattered trees).The results also indicate that beyond the intrinsic physical properties of the LCZs of a city,their area proportions cannot be overlooked in evaluating their impact on the UHI and UDI.These quantitatively findings could help urban planners to create a livable urban climate and environment by adjusting the relevant land use.