Economic evaluation of HVAC systems with ice storage designed using an optimization technique

Thermal energy storage (TES) is recognized as an important technique for energy management in heating, ventilation and air conditioning (HVAC) systems. This paper discusses the economic aspects of the optimal design for such systems. The model for optimal design so determines the sizes of the main components of the system - namely the chiller and the storage tank - that the system's life cycle cost is minimal. The model is based on linear programming and is implemented in a computer program for HVAC systems with ice storage. This paper demonstrates that the optimal sizes of chiller and storage tanks differ from those selected using traditional techniques. It emphasizes the cost-effectiveness of the optimally designed system and also includes a sensitivity analysis pertaining to the economic feasibility of such systems under different economic conditions.     

A Swedish investigation of arson

After correction, a Swedish investigation of selected crimes of arson reported to the police in 1988 revealed 6,327 incidences of arson, or 0.075% arson fires per capita, for that year. Based on estimates of the dark factor, which is the ratio between the actual number of crimes and those reported, and on the rising trends, the figure over the next few years is not likely to exceed 0.12%. Using material provided by insurance companies, a total loss volume of Swedish crowns (SEK) 1.1 ± 0.1 × 1000 m, or about U.S. $160 + 16 m, was calculated after correction; this corresponds to 0.09% of the Gross National Product.The loss that resulted from the different types of arson was distributed by size according to the lognormal distribution function. Vandalism accounted for 55% of the incidents and 23% of the cost, while arson committed in connection with another crime accounted for 6% of the incidents and 15% of the cost. Revenge, spite, and conflicts accounted for 5% of the incidents and 10% of the cost. Mental illness accounted for 4% of the incidents and 6% of the cost. And arson for which the motive was unknown accounted for 23% of the incidents and 36% of the cost.Most of the arson fires were set in containers, refuse storage rooms, basements, attics, and so on. Fewer arson fires occurred in commercial properties, but these accounted for a greater proportion of the loss. This was also true for enterprises, dwellings, and schools.Fifty percent of the arson was committed by children and people under age 18, a figure that appears likely to increase. For minor property damage, the figure was 60%, and the rising trend there was more pronounced. A breakdown of arson over the period 1979–1988 by police districts with different population densities showed that the frequency of arson increases as population density increases, particularly for minor property damage. A breakdown of the material for Stockholm by districts clearly showed a higher frequency of arson in problem areas and a lower frequency of arson in high-status areas.     

小型气力垃圾输送系统的设计与应用研究

近年来气力垃圾输送系统作为一种新型的节能环保科技已在国内多个新城市和医院等大型建设项目中获得成功应用,但在小型住宅项目中由于系统设计、配套、造价等问题一直难以推广和应用。文章针对小型住宅建设工程的项目特点,结合大型系统的工程实践经验,对小型气力垃圾输送工程应用的系统负荷进行了理论计算,并对系统中的中央收集站、垃圾储存和管网设备进行了优化设计,推出了小型住宅项目的系统设计和应用模型,从而简化系统设备构造,降低系统实施的土建配套要求,同时也减少了系统设备投资造价,对小型系统的实际应用具有重要的指导意义。     

垃圾处理工程中垃圾坝设计技术探讨

本文对城市生活垃圾处理工程中的垃圾坝 ,就其结构设计技术作了多方面的探讨通过工程实践总结 ,提出了优化设计 ,降低工程造价的 8项措施 ,供有关设计人员参考     

Optimization of steel floor systems using particle swarm optimization

Particle swarm optimization (PSO) is used for the design of composite and non-composite steel floor systems. The design problem is the minimization of the mass or the cost of a steel floor configuration subject to constraints related to the Canadian S16 design standard. The PSO algorithm was applied to three different steel floor bays. Outputs returned are the girder and beams sizes, steel deck profile, concrete slab thickness, number of interior beams and the number of steel studs needed per beam. Results show the PSO can consistently find the optimum floor configuration by minimizing the total mass or cost while satisfying all design criteria.     

A model to study the effects of time-variable pollutant loads on stream quality

A deterministic computer model has been proposed to study the effects of discharges from combined sewer drainage areas on receiving bodies of water. The model provides capability for studying the effects of varying treatment plant capacity, interceptor sewer capacity and storage on stream quality. The operating parameters for the storage vessel are defined in detail. A cost function for all system components is included in the model.

The variation of total mass phosphate discharge, peak instantaneous phosphate concentration and cost with the variation of the various system parameters is reported for a series of model runs on three drainage areas.     

Sampling and storage of natural waters for trace metal analysis

Methods for the collection, preservation and storage of natural water samples for the analysis of trace levels of heavy metals have been critically reviewed, with particular reference to the analysis of zinc, copper, lead, cadmium and mercury. Recommended prodecures are given which minimise the problems of sample contamination and adsorption losses. Carefully cleaned high-density polythene or Teflon containers are recommended for both sampling and storage, with a storage temperature of 4°C. Acidification to 0.05 M H⁺ with nitric acid is desirable, except in speciation studies. For mercury analysis the addition of an oxidant or complexing agent is also necessary.     

Hydraulic permeability of structures made of geotextile sand containers: Laboratory tests and conceptual model

The permeability values were obtained for more than 15 different geotextile sand container (GSCs)-structures. The influence of the size of the sand containers (four different sizes were tested), arrangement and geometry was investigated. First results show that the size of the container represents one of the primary factors influencing the permeability but the method of placement of the GSCs also plays a significant role (different methods of placing resulted in a permeability with more than a 50% difference). The results show that the flow through the GSC-structure is solely governed by the gaps between neighbouring containers and that the flow through the sand fill in the containers can be neglected.In addition, several GSC-structures with the same geometry and the same size of containers but with different arrangements (and thus different permeabilities) were tested under wave action in the twin wave flume of LWI. The results show that the mode of placement of elements strongly affects the permeability and the stability of GSC-structures. Placement of the containers in such a way that the contact areas among containers are maximized resulted in the largest overall stability against wave action. A conceptual model for the determination of the permeability of GSC-structures is proposed.     

Pollutant emissions from vehicles with regenerating after-treatment systems in regulatory and real-world driving cycles

Regenerating exhaust after-treatment systems are increasingly employed in passenger cars in order to comply with regulatory emission standards. These systems include pollutant storage units that occasionally have to be regenerated. The regeneration strategy applied, the resultant emission levels and their share of the emission level during normal operation mode are key issues in determining realistic overall emission factors for these cars. In order to investigate these topics, test series with four cars featuring different types of such after-treatment systems were carried out. The emission performance in legislative and real-world cycles was monitored as well as at constant speeds. The extra emissions determined during regeneration stages are presented together with the methodology applied to calculate their impact on overall emissions. It can be concluded that exhaust after-treatment systems with storage units cause substantial overall extra emissions during regeneration mode and can appreciably affect the emission factors of cars equipped with such systems, depending on the frequency of regenerations. Considering that the fleet appearance of vehicles equipped with such after-treatment systems will increase due to the evolution of statutory pollutant emission levels, extra emissions originating from regenerations of pollutant storage units consequently need to be taken into account for fleet emission inventories. Accurately quantifying these extra emissions is achieved by either conducting sufficient repetitions of emission measurements with an individual car or by considerably increasing the size of the sample of cars with comparable after-treatment systems.     

Low temperature heat storage with phase change materials

A group of promising phase change heat-storage materials was selected through study of the literature, laboratory tests of freeze—melt behaviour and determination of thermophysical properties. Means were developed of encapsulating these materials in metal or plastic containers. Four of these phase-change materials, suitably encapsulated, were tested in a sub-kale thermal storage unit of about 20MJ capacity, using air as the heat-transfer fluid. In most cases, measured thermal-storage capacity exceeded 90% of the theoretical value. After considering a number of heating and cooling schemes employing phase-change heat storage, we selected a forced hot air, central storage design, using CaCl₂.6H₂O encapsulated in plastic pipes. A home was designed, using a two-storey conservatory for solar collection with vertical glazing and movable insulation.     

西安市暴雨强度公式的推导与研究

采用座标抄录自记雨量资料，１ａ多次法选样，以指数型频率分布配合，经编制程序上机寻优确定ｂ值等计算，推导出西安市新编制的暴雨强度公式ｉ＝。经误差分析及新旧公式对比，发现新公式精度高，符合西安市暴雨实际情况。     

上海城市生活垃圾集中分选资源化模式研究

为了探究上海城市生活垃圾资源化模式,试验采用方孔径为120、40、8 mm的3种手动筛,对垃圾进行筛分,并对筛分后不同粒径的垃圾进行了分类.结果表明;粒径为40～120 mm的垃圾含量最大,试验的平均百分比约为43.5%;其次是粒径为8～40 mm的垃圾,平均百分比约为34.9%;粒径>120 mm的约为15.7%;粒径<8 mm的约占5.8%.随着粒径的变小,可生物降解有机物含量增加,塑料含量降低.12类垃圾中,可堆肥的有机垃圾约占65%;可焚烧垃圾(塑料、纸类、纺织物、包装物、木块和部分余下物),约占30%;可回收二次利用的垃圾(玻璃、铁金属和非铁金属),约占2.5%;有毒有害垃圾约占0.39%;剩余的无机垃圾量不足3%.试验结果表明,此方式为上海提供了一个生活垃圾集中分选资源化模式.     

Application of spherical tuned liquid damper in vibration control of wind turbine due to earthquake excitations

A spherical tuned liquid damper (TLD) is proposed as a cost‐effective method to reduce the earthquake‐induced vibration of wind turbines. A 1/20‐scale test model was designed to investigate its performance of controlling the structural vibration. A series of free and forced vibration experiments with different water depths in hemispherical containers were performed on the shaking table. Three measured ground acceleration‐time histories, including El Centro NS, El Centro EW and Tianjin EW, were selected to verify the effectiveness of spherical TLD in suppressing the earthquake‐induced vibration. The experimental results showed that the spherical TLD could effectively improve the damping capacity of the test model. The standard deviation of the dynamic response could be effectively reduced when the excitation frequency was approximately equal to its fundamental frequency. The liquid sloshing motion in containers was characterized by a highly nonlinear and complex nature. The effectiveness of spherical TLDs does not increase linearly as the mass of water in containers and is influenced greatly by the frequency components of earthquake excitations. For El Centro EW excitation, the standard deviations of the dynamic responses could be reduced more than 40% when the liquid mass was about 2% of the generalized mass. Copyright © 2015 John Wiley & Sons, Ltd.     

The practicality of distributed PV-battery systems to reduce household grid reliance

The advent of low-cost solar photovoltaics (PV) and battery electricity storage has the potential to bring about fundamental shifts in the structure of the power sector in the United States. We analyze how PV-battery systems of various sizes could reduce the dependence of residential customers on the central grid and their impact on CO₂ emissions. We further analyze how the costs of such systems change as customers attempt to decrease their dependence on the grid, considering the installed cost of PV-battery systems and the cost of electricity under a net-energy metered rate structure. We analyze these relationships for residential customers in five locations across the U.S. We find that fully disconnecting from the grid with a PV-battery system is impractical for most residential customers without also having dispatchable backup generation. Finally, we estimate how the economics of behind-the-meter PV-battery systems may change if the costs of PV systems continue to fall.     

Optimum fleet size determination by queuing and simulation

Queuing theory applications in the field of earth-moving operations are reviewed. Using queuing theory and simulation techniques, a model is developed that can predict the productivity of one pusher and a fleet of scrapers under a given set of operating conditions. A computer program is developed for this purpose that interfaces Gaarslev's Queuing Model Program and Caterpillar's Vehicle Simulation Program. The new system can consider the effect of variable inter-arrival times and bunching and road and machine conditions. The developed computer system allows the user to perform a sensitivity analysis by varying the number of scrapers, thus determining the optimum fleet size based on the lowest cost per cubic yard of production.     

公路沿线遭遇滚石的风险分析——方法研究

随着中国经济建设的迅速发展，山区内大量公路将面临着越来越多的滚石问题。显然，公路沿线遭遇滚石的风险分析对滚石灾害的分区与防治资金的优化配置是十分重要的。在工程地质力学综合集成方法论（EGMS）的指导下，由现场调查、专家经验、理论分析等结合得到了困难条件下滚石发生频率的估计方法。假定一个滚石区范围内的人类活动和潜在滚石在时间和空间上为均匀分布，利用贝努力公式给出了静止车辆、移动车辆、行人等情况下遭遇滚石的概率计算方法。由遭遇滚石的概率及承灾体的易损性分析，可进一步得到公路上车辆和行人经过不同滚石区时受滚石冲击而致命的风险水平。     

Assessing farmers' practices on disposal of pesticide waste after use

Common practices of farmers on disposal of pesticide waste after use were surveyed in five regions of the rural area of Pieria in northern Greece using a structured questionnaire administered via personal interviews. Concerning leftover spray solutions, most farmers reported that they normally re-spray the treated field area until the spraying tank is empty (54.9%) or they apply the leftover spray solutions to another crop listed on the product label (30.2%). A minority of the farmers (4.3%) mentioned that they often release the leftover spray solutions near or into irrigation canals and streams. As regards rinsates generated from washing the application equipment, most farmers reported that they release the rinsates over a non-cropped area (45.7%) or they drop the rinsates near or into irrigation canals and streams (40.7%). Moreover, a great proportion of the farmers stated that they dump the empty containers by the field (30.2%) or they throw them near or into irrigation canals and streams (33.3%). Burning the empty containers in open fire (17.9%) or throwing the empty containers in common waste places (11.1%) was also reported. Several farmers stated that they continue to use old pesticides for spraying (35.8%). Training programs which raise awareness of farmers of the potential hazards of pesticide use and particularly of the proper management of waste products, recycling programs and collection systems for unwanted agricultural chemicals to prevent inappropriate waste disposal, as well as improving packaging of pesticides to minimize waste production are essential for promoting safety during all phases of pesticide handling.     

上海长江大桥车桥系统节段模型涡激共振试验研究

涡激共振通常都在低风速发生,且涡激共振对断面形式的微小变化很敏感,因此有必要研究车辆对车桥系统涡激共振性能的影响。以上海长江大桥为背景,在同济大学土木工程防灾国家重点实验室TJ-1边界层风洞中进行了1∶60缩尺模型试验,开展了桥面无车状态、桥面有车状态下的两种断面形式以及0°、 3°和-3°三种风攻角共6个试验工况节段模型涡激共振试验研究,并将模型试验结果经过振型修正换算到实桥。试验结果表明:桥面有车状态下的竖弯涡振和扭转涡振中分别伴有相同频率的扭转振动和竖弯振动;桥面有车状态的竖弯涡振和扭转涡振幅值明显比桥面无车状态大;桥面有车状态下的涡振锁定风速区间比桥面无车状态下提前。可见车辆明显改变了主梁的气动外形,且无论从振幅还是振动形态方面考虑,车辆对车桥系统的涡激共振影响是不可忽视的。     

Real-time simulation using graceful degradation of accuracy

Real-time computer simulation is required in a number of applications, where the simulated dynamic systems are directly coupled with systems in the real world or with other systems also running in real-time. Typical problems of real-time simulations are that the dynamics of the modeled system are not represented in enough detail, either by not sampling the inputs or not producing output values frequently enough or both. Increasing the sampling frequencies may lead, as an additional problem, to real-time violations caused by insufficient computing power. The latter problem is amplified if the real-time is accelerated to achieve a kind of fast motion and reduce experiment times. In this paper, we show how the first problem can be solved by automatic frequency adjustment, minimizing the number of computations and how the remaining second problem can be reduced by trading a graceful degradation of accuracy against the computing power requirements automatically. Experiments show that simulation times could be reduced by a factor of 100 without unacceptable simulation errors.     

Regrowth and survival of indicator microorganisms on the surfaces of household containers used for the storage of drinking water in rural communities of South Africa

The present study covered two rural communities of South Africa: Ncera and Ntselamanzi villages. Raw water from Ncera river is used by the community of Ncera village for drinking, while the community of Ntselamanzi receives their drinking water from Alice purification system. Treated water is supplied to the community by a public standpipe system. In rural communities of South Africa, many households use polyethylene (PE) and galvanized steel (GS) containers for the storage of their drinking water. To investigate the regrowth and survival of indicator microorganisms on the surface of household containers during the storage of drinking water, PE and GS slides were suspended in the appropriate household containers for a period of 48 h. This period of 48 h was chosen as the study period because results from the questionnaire indicated that the largest percentage (62%) of households store their water for that length of time. The experiment was performed to test drinking water as it is collected and stored by rural communities. No disinfection of household containers or slides was done during the study period. Attached coliphages (F-RNA (FP) and somatic phage (SP), coliform bacteria (total coliform (TC), presumptive Escherichia coli (EC), Salmonella (Sal) and Clostridium perfringens (CP) were measured during the study period. With the exception of CP, attached indicator microorganisms consisted of TC, presumptive E. coli and Salmonella, somatic and F-RNA coliphages, although the yield (average count) for the last four groups (EC: < 1-3 cfu cm(-2), Sal: < 1-15 cfu cm(-2), FP: < 1-7 pfu cm(-2), SP: < 1-7pfu cm(-2)) was lower than that of TC (3-183 cfu cm(-2)). However, the lowest yield of indicator microorganisms was noted for presumptive E. coli. Whereas the occurrence and survival of TC was noted on the surface of household containers during the entire period of the experimental study, other indicator microorganisms occurred from time to time. The regrowth of indicator microorganisms occurred 48 h after the exposure of slides to both types of test waters. This length of time mostly resulted in the regrowth of TC (with an increase in bacterial counts) while the persistence of other indicator organism groups on the surface of the slides was apparent. A comparison between PE and GS containers showed that more TC (average count) regrew on PE than on GS containers (for river water, PE: from 36 to 55 cfu cm(-2), GS: from 25 to 26 cfu cm(-2); for standpipe water, PE: from 147 to 183 cfu cm(-2), GS from 3 to 4 cfu cm(-2)). This study revealed that both types of household containers supported the growth and survival of indicator microorganisms due to the bad quality of the intake water before storage. The storage of drinking water for 48 h mainly resulted in the regrowth of TC. Nevertheless, the persistence of other indicator microorganisms was observed on the surface of household containers.