Characteristics Of Buffers Research Articles

A hybrid conductometric/spectrophotometric method for determining ionic strength of dilute aqueous solutions

This work describes a novel conductometric/spectrophotometric method to determine the ionic strength (I) of dilute aqueous solutions (e.g., natural waters from rivers and lakes). Because I ≤ 0.01 mol kg−1 in such waters, precision as well as accuracy is of paramount importance. In current practice the ionic strength of natural waters is determined almost exclusively with conductometric measurements. We used solutions of artificial freshwater to assess the performance of two commonly used types of conductometric instruments and found that a conductivity probe systematically overestimated I while a salinometer systematically underestimated I. We therefore recommend here an empirical correction that can be easily implemented to improve the accuracy of both types of conductivity measurements. Additional improvement in measurements of I can be achieved by using that high-quality conductometric measurement as input to a hybrid conductometric/spectrophotometric procedure that makes use of robust quantitative characterizations of the influence of ionic strength on the dissociation characteristics of phosphate pH buffers and sulfonephthalein pH indicators. This approach mitigates systematic conductometric errors associated with solution composition, thus yielding measurements of ionic strength with substantially improved accuracy and precision. The method was validated by testing on a broad suite of artificial freshwaters (n = 64) with compositions that include the major ions present in dilute natural waters (Na+, K+, Mg2+, Ca2+, Cl−, HCO3−, and SO42−). This new hybrid method is applicable to waters of 0 ≤ I ≤ 0.01 mol kg−1 (i.e., electrical conductivity of up to 900 μS cm−1 at 25 °C), with an accuracy of ±0.0003 and a precision of ±0.0003.

GEOPOLITICS OF IRAN ACCORDING TO THE THEORY OF GEOGRAPHICAL BUFFER SPACES

With the occupation of India by one of the global powers namely Britain (1770), and its territorial expansion toward the West and Iran’s borders, Russia (the other global power) started to expansionism and move toward Indian Ocean and Iran’s north borders from the first of 19th century (1804-1813/ 1826/1828). Britain from East and South and Russia from North intruded on Iran’s borders, and buffered Iran and Afghanistan in order to not to collide with each other. In the rivalry pattern of buffered states, their geographic spaces should be separate. Low power geographic space is required between the powers. Geopolitical boundaries of these two powers should not contact because in such a case, the possibility of conflict can arise. So, the buffer space takes the form of vacuum space between the buffered powers.The research main question is that what are the nature, functions, characteristics and political behavior of geographic buffer space? Which geographic values and functions cause buffer space act as a buffer space and attract great powers?In this research, a new definition of buffer space is presented, and the process of formation of buffers (the whys and wherefores), functions and characteristics of buffers in two internal and external dimensions are investigated. Then, the validity of the variables is investigated using library and field findings, and is used in the process of evaluation of internal and external experts. The results are analyzed using statistical methods and SPSS. Finally, these variables are evaluated in the context of Iran.The research findings show that the pattern of geopolitical rivalry of great powers has been reflected in Iran’s space in the last two centuries, namely not only foreign relations, but also Iran’s internal political situation are reflections of the pattern of rivalry of great powers resulted from Iran’s buffer situation. The behavior of Iranian politicians and people have been affected by the behavior of buffered powers. This situation has caused some behaviors to be created like xenophobia, lack of trust in politicians, de-utilization etc. The buffer space cannot make decision without considering the interests of buffered states. In the buffer space, all of the political phenomenon are the reflection of buffered space.

How urban densification promotes walking for transportation in older community dwellers of an Asian metropolis

OPS 58: Predictors and impact of active travel, Room 210, Floor 2, August 28, 2019, 10:30 AM - 12:00 PM Background/Aim: Urban density has been linked to higher levels of walking for transport. However, the factors and pathways responsible for these associations are unclear. Also, most findings on this topic are from locations with low-to-moderate levels of density. This study examined potential mechanisms underpinning the effects of urban densification on walking for transport in older community dwellers of an ultra-dense Asian city. Methods: The Active Lifestyle and the Environment in Chinese Seniors (ALECS) study is an epidemiological study on the environmental correlates of older Hong Kong community dwellers’ walking and mental health. 909 participants were recruited from neighbourhoods stratified by income and walkability. Geographic Information Systems quantified dwelling density and other environmental characteristics (e.g., parks and destination density) of street-network buffers surrounding participants’ homes. Data on within- and outside-neighbourhood walking for transport, socio-demographic characteristics and health were collected using interviewer-administered questionnaires. Directed Acyclic Graphs and Generalised Additive Mixed Models were used to examine the total, mediated and unmediated effects of dwelling density on walking. Results: Total effects indicated that dwelling density was positively associated with measures of within-neighbourhood walking. The effect of dwelling density on frequency of within-neighbourhood walking was fully mediated by food outlets/retail density, entertainment density, car ownership and health conditions (via road intersection density). The effect of dwelling density on amount of within-neighbourhood walking was partly mediated by similar environmental factors directly and indirectly via their effects on frequency of within-neighbourhood walking. Transportation density was a suppressor. Complex mediated and suppression effects of dwelling density on measures of outside-neighbourhood walking were also observed. Conclusions: The potential effects of urban densification on walking for transport in Hong Kong older adults are complex and include mediating factors exerting non-linear influences of opposite direction. A better understanding of these can inform the creation of healthy and age-friendly cities.

Physical function as a moderator of associations between neighbourhood environments and neighbourhood (dis)satisfaction in older adults

TPS 701: Spatial determinants of population health, Exhibition Hall, Ground floor, August 27, 2019, 3:00 PM - 4:30 PM Background/Aim: As neighbourhood satisfaction has been positively associated with health or health-related outcomes such as mental health, self-efficacy and physical activity, it’s imperative to develop the currently limited understanding of neighbourhood environment influences on neighbourhood satisfaction. This study examined associations between objectively-measured environmental attributes and neighbourhood (dis)satisfaction and the moderating effect of physical function in Hong Kong and Ghent (Belgium) older adults. Methods: Participants were older adults from comparable epidemiological studies conducted in Hong Kong and Ghent. Participants were recruited from neighbourhoods stratified by socio-economic status and walkability. Environmental characteristics of street-network buffers around participants’ homes were quantified by Geographic Information Systems. Comparable measures of neighbourhood satisfaction, socio-demographics and physical function (objective) were used. Generalised Additive Mixed Models were used to determine associations between neighbourhood environment characteristics and neighbourhood satisfaction as well as moderating effects of physical function and city. Results: Linear or curvilinear negative associations were observed between neighbourhood dissatisfaction and objectively-assessed density of services, recreational facilities, public transport stops and number of parks (1km buffers). Distance to the nearest park and public transport stop were positively linearly related to neighbourhood dissatisfaction, while intersection density and number of parks within 400m residential buffers were negatively related to neighbourhood dissatisfaction. No significant associations were observed with park area and dwelling density. Most environmental attributes had similar associations across the two study sites, with the exception of recreational facilities and distance to the nearest public transport stop. Physical functionality did not moderate any of these associations. Conclusions: Objectively-assessed neighbourhood environmental characteristics are important contributors to older adults’ satisfaction with their residential neighbourhoods irrespective of physical functionality levels. Most of these effects seem to be generalisable across very different geographical and cultural contexts.

ВИСОКОЛІНІЙНІ БУФЕРИЙ МАСШТАБАТОРИ НАПРУГИ НА БІПОЛЯРНИХ ТРАНЗИСТОРАХ ІЗ НИЗЬКИМ ВХІДНИМ СТРУМОМ

Buffer devices and voltage scalers are widely used in various analog-digital systems, when it is necessary to match the signal in the form of voltage from a low-power sensor to a load, it consumes significantly more power. In this case, the voltage buffer is characterized by a voltage transfer coefficient close to unity, and must also have a high input resistance and sufficient load capacity. The voltage scaler, in contrast to voltage buffers, must additionally provide the necessary gain transfer ratio, which can be substantially more than one. The circuit design features of three variants of the construction of voltage buffer cores and voltage scaling are considered. It is proved that it is advisable to reduce the input zero bias current by using amplifying n-p-n and p-n-p transistors, as well as Shiclay transistors in the input stages. The static and dynamic characteristics of the voltage buffers and the voltage scaler must meet the system requirements of the device. The static characteristics should be attributed primarily to the error of the transfer characteristics of the scale, zero offset and linearity. The dynamics of these devices is determined by the frequency response and transient response. Static and dynamic characteristics are analyzed by computer simulation where it is shown that the scale errors of the voltage buffers and the voltage scaler do not exceed 10 µV in the range of the corresponding signal ± 5 V, and the linearity errors are 300 nV. A transient response was obtained which states that the slew rate of the output voltage will be no worse than 2000 V/µs. A comparison of the metrological characteristics of the voltage buffers and the voltage scaler in the form of a set of cores and output push-pull DC amplifiers. It is proved that the use of these amplifiers allows significantly (by 3-4 orders of magnitude) to improve the load capacity of the circuits while maintaining the level of the input zero bias current, as well as scale and linearity errors.

Experimental investigation of the quasi-static and impact tests on the energy absorption characteristics of coupler rubber buffers used in railway vehicles

Coupler rubber buffers are widely used in high-speed trains, to dissipate the impact energy between vehicles. The rubber buffer consists of two groups of rubbers, which are pre-compressed and then installed into the frame body. This paper specifically focuses on the energy absorption characteristics of the rubber buffers. Firstly, quasi-static compression tests were carried out for one and three pairs of rubber sheets, and the relationship between the energy absorption responses, i.e. Eabn = n × Eab1, Edissn = n × Ediss1, and Ean = Ea1, was obtained. Next, a series of quasi-static tests were performed for one pair of rubber sheet to investigate the energy absorption performance with different compression ratios of the rubber buffers. Then, impact tests with five impact velocities were conducted, and the coupler knuckle was destroyed when the impact velocity was 10.807 km/h. The results of the impact tests showed that with the increase of the impact velocity, the Eab, Ediss, and Ea of the rear buffer increased significantly, but the three responses of the front buffer did not increase much. Finally, the results of the impact tests and quasi-static tests were contrastively analyzed, which showed that with the increase of the stroke, the values of Eab, Ediss, and Ea increased. However, the increasing rates of the impact tests were higher than that of the quasi-static tests. The maximum value of Ea was 68.76% in the impact tests, which was relatively a high value for the vehicle coupler buffer. The energy capacity of the rear buffer for dynamic loading was determined as 22.98 kJ.

Neighborhood-based PA and its environmental correlates: a GIS- and GPS based cross-sectional study in the Netherlands

BackgroundTo improve our understanding of the neighborhood environment – physical activity (PA) relationship, it is of importance to assess associations between neighborhood environmental characteristics and neighborhood-based PA.MethodsParticipants’ (N = 308; 45–65 years) light PA (LPA) and moderate-vigorous PA (MVPA) within a 400, 800, and 1600 m buffer around adults’ homes was measured using accelerometers and GPS-devices. Land use data in ArcGIS provided neighborhood characteristics for the same buffers. Multilevel linear regression models, adjusted for socio-demographic variables and attitude towards PA, were used to assess associations of objective neighborhood characteristics with neighborhood-based LPA and MVPA.ResultsLPA was positively associated with the proportions of roads (within a 400 m buffer), and negatively associated with the proportions of recreational areas (within an 800 m buffer), and the proportion of green space (within the 800 m and 1600 m buffers). Multiple characteristics of 400 m buffers were positively associated with MVPA, i.e. proportions of green space, blue space, residences, shops and foodservice industry, sports terrain, and public social-cultural facilities. Also, characteristics of larger buffers were positively associated with MVPA, i.e. the proportions of shops and foodservice industry, sports terrain, and blue space (within an 800 m buffer), and the proportion of public social-cultural facilities (within the 800 m and 1600 m buffers).ConclusionsObjective neighborhood characteristics of smaller as well as larger sized buffers were associated with neighborhood-based LPA and MVPA. Green and blue spaces seem to be of particular importance for PA in the smallest buffer, i.e. in the direct surrounding of adults’ homes.

Performance Simulation of High Capacity Hydrostatic Buffer with Silicone Gum

재사용이 가능한 철도차량용 버퍼는 가스-유압식 완충기가 널리 사용되어 오고 있으나, 최근 몇 년 동안에 실리콘 검을 사용한 정수압 완충기에 대한 요구가 점차 커지고 있다. 실리콘 검은 스프링과 유사한 압축 특성을 가지고 있으며, 고점도 층류 유동에 따른 감쇠 특성도 가지고 있다. 높은 예하중을 갖는 완충기에 적합한 실리콘 검 완충기는 단순한 디자인과 간편한 유지보수 등의 이점이 있다. 실리콘 검 완충기의 동적 특성을 해석하기 위해, 본 논문에서는 연속 방정식, 피스톤과 실린더 바디 사이의 환형 틈새에서 전단 박하특성을 갖는 비뉴톤 유체의 압력과 유량 관계식, 하드 패킹에서의 마찰력을 포함하는 운동 방정식을 적용한 수학 모델을 제시하였다. 또한 정수압 검 완충기의 동적 완충력을 해석하고 TÜ V 충돌 시험 결과와 해석 결과를 비교하였다.

Parametric study of the distribution of longitudinal dynamic forces developed in the train body using hysteretic characteristics of Ringfeder buffers

During braking, due to the interaction between the vehicles, longitudinal dynamic forces, characterized by different values and an irregular distribution along the train, develop in the train body, affecting the passengers` comfort or even the traffic safety. The paper is a parametric study having as objective to determine the influence of the number of coaches, vehicle weight and delay time of the development of braking forces on the size and distribution of the longitudinal dynamic forces developed in passenger trains during braking. The first analysis is based on the change in the number of vehicles which are part of the train. The second case analyzed refers to the total mass of the vehicles, which increases by 50% compared to standard train mass. In the third situation, there are taken into account variations of ± 20% of the length of the train overall pipe that are able to generate delays related to the occurrence and development of the braking forces at each vehicle of the train body.

Blocking Probability Simulations for FDL Feedback Optical Buffers

Asynchronous optical packet switching seems to a suitable transport technology for the next-generation Internet due to the variable lengths of IP packets. Optical buffers in the output port are an integral part of solving contention by exploiting the time domain. Fiber delay lines (FDLs) are a well-known technique for achieving optical buffers, and various optical buffer architectures using FDLs have been proposed. These are generally classified into two types of structure: feed-forward (FF) or feedback (FB). In the FF buffers, optical packets are delayed at the output ports by passing through step-increasing-length multiple FDLs to avoid contentions, and in the FB buffers, optical packets are delayed by being fed back in re-circulating loop FDLs to avoid contentions. We report the detailed characteristics of optical FB buffers with the Post-Reservation (PostRes) policy and clarify the superiority of the FB buffers through simulations. For comparison, we also show the characteristics of FBSI (FB with step-increasing-length FDLs) and FF buffers. We found that 1) the blocking probabilities in the FB buffer were about 10-2 lower than those in the FF buffer and 2) the blocking probabilities for the deterministic case in the FB buffer sharply dropped at D=1.0, where the packet length was equal to the FDL loop length. We carried out 108 packet simulations. The results can be applied to the design of WDM optical packet switches and networks with the maximum throughput.

Racial/Ethnic Differences in Household Loan Delinquency Rate

This study investigates the differences in household loan delinquency rates of racial/ethnic groups. The study examines the role of demographic and socioeconomic characteristics of households, financial buffers, economic and financial triggers, high debt service ratio, and credit constraint in household delinquency. The study uses combined data from 2001, 2004, 2007, and 2010 Surveys of Consumer Finances (SCF). Having combined data allowed the separation of African Americans from Hispanics in this study. We employed both logistic regression and Blinder-Oaxaca decomposition analysis. The use of combined data from four survey years ensures the robustness of statistical results and analysis. The findings show that events that constitute shocks or triggers to households have a more significant impact on delinquency rate. The study found that payday loan borrowers are 4.6 times more likely to be delinquent on their loans than non-payday loan borrowers between 2007 and 2010. Also, the study finds significant statistical difference of delinquency rates among the racial/ethnic groups. Our results show that high debt service ratio (DSR) and being credit constrained have significant impact on the delinquency rates for all races. The results obtained showed that 59.96 % of the difference in delinquency between Whites and African Americans is explained by endowments, while 40.04 % is unexplained. Similarly, 97.35 % of the difference in delinquency between Hispanics and whites is explained by endowments, while 2.65 % of the difference is unexplained or is attributable to discrimination.

A Novel Algorithmic Approach to Aid Post-Silicon Delay Measurement and Clock Tuning

The number of speedpaths in modern high-performance designs is in the range of millions and, due to unmodelled electrical effects, they are difficult to be measured accurately before the first silicon samples are available. As a consequence, clock tuning elements are employed to aid the post-silicon clock tuning. However, as the number of these elements continues to grow, it becomes increasingly difficult to determine their configurations in a compute effective manner. In this paper we describe a novel exact algorithm for post-silicon clock tuning, which employs smart pruning techniques that exploit the characteristics of the clock tuning buffers.

A digital photography protocol for the rapid assessment of herbaceous communities in riparian buffers

AbstractClose-range digital photography is a promising tool for monitoring plant communities, yet this technology has not been used to indicate changes to the compositional and functional characteristics of riparian vegetation buffers in agro-ecosystems. We tested a photographic protocol using image indices to monitor differences in the compositional (species diversity) and functional characteristics (plant height, flowering and leaf traits) of 28 herbaceous communities repeatedly surveyed over an entire growing season. Specifically, we used known vegetation properties to predict image texture and geometric patterns. Our results revealed that image texture decreased with increasing plant height, leaf polyphenol content and species diversity. Low texture values in close-range digital images were typically found in tall, flowering, and functionally diversified assemblages consisting mostly of forbs species. In contrast, species assemblages dominated by grasses or sedges presented more random geometric patterns and images with higher texture values. Further tests of this photographic protocol will have to explore other image indices and extend its application to other ecosystems.

Describing the access network by means of router buffer modelling: a new methodology.

The behaviour of the routers' buffer may affect the quality of service (QoS) of network services under certain conditions, since it may modify some traffic characteristics, as delay or jitter, and may also drop packets. As a consequence, the characterization of the buffer is interesting, especially when multimedia flows are transmitted and even more if they transport information with real-time requirements. This work presents a new methodology with the aim of determining the technical and functional characteristics of real buffers (i.e., behaviour, size, limits, and input and output rate) of a network path. It permits the characterization of intermediate buffers of different devices in a network path across the Internet.

Buffer capacity of biologics—from buffer salts to buffering by antibodies

Controlling pH is essential for a variety of biopharmaceutical process steps. The chemical stability of biologics such as monoclonal antibodies is pH-dependent and slightly acidic conditions are favorable for stability in a number of cases. Since control of pH is widely provided by added buffer salts, the current study summarizes the buffer characteristics of acetate, citrate, histidine, succinate, and phosphate buffers. Experimentally derived values largely coincide with values calculated from a model that had been proposed in 1922 by van Slyke. As high concentrated protein formulations become more and more prevalent for biologics, the self-buffering potential of proteins becomes of relevance. The current study provides information on buffer characteristics for pH ranges down to 4.0 and up to 8.0 and shows that a monoclonal antibody at 50 mg/mL exhibits similar buffer capacity as 6 mM citrate or 14 mM histidine (pH 5.0-6.0). Buffer capacity of antibody solutions scales linearly with protein concentration up to more than 200 mg/mL. At a protein concentration of 220 mg/mL, the buffer capacity resembles the buffer capacity of 30 mM citrate or 50 mM histidine (pH 5.0-6.0). The buffer capacity of monoclonal antibodies is practically identical at the process relevant temperatures 5, 25, and 40°C. Changes in ionic strength of ΔI=0.15, in contrast, can alter the buffer capacity up to 35%. In conclusion, due to efficient self-buffering by antibodies in the pH range of favored chemical stability, conventional buffer excipients could be dispensable for pH stabilization of high concentrated protein solutions.

Migration behaviour of discontinuous buffers in capillary electrophoresis during protein enrichment

Capillary electrophoresis (CE) is not only an effective separation technique, but can also serve as a sample preparation tool for enrichment and purification at sub-microliter sample volumes. Our approach is based on the use of a discontinuous buffer system consisting of an acid and a base (acetate and ammonium). Proteins and/or peptides with isoelectric points between the pH values of these two buffers will become stacked at the neutralization reaction boundary (NRB). To understand the mechanism of the NRB formation and the electrophoretic migration of various ions during the enrichment, we performed experiments using myoglobin and mesityl oxide to reveal the ion migration patterns at the buffer junction, and utilized Simul 5 to computer simulate the process. The simulated results closely resembled the experimental data, and together, they effectively revealed the characteristics of the discontinuous buffers. Importantly, the discovery allowed the manipulation of NRB behaviours by controlling the discontinuous buffer composition. To illustrate this, the removal of urea as an unwanted background molecule from the enriched protein sample was achieved based on the acquired information.

The Role of Optics and Electronics in High-Capacity Routers

This paper examines the role of optical and electronic technologies in future high-capacity routers. In particular, optical and electronic technologies for use in the key router functions of buffering and switching are compared. The comparison is based on aggressive but plausible estimates of buffer and switch performance projected out to around 2020. The analysis of buffer technologies uses a new model of power dissipation in optical-delay-line buffers using optical fiber and planar waveguides, including slow-light waveguides. Using this model together with models of storage capacity in ideal and nonideal slow-light delay lines, the power dissipation and scaling characteristics of optical and electronic buffers are compared. The author concludes that planar integrated optical buffers occupy larger chip area than electronic buffers, dissipate more power than electronic buffers, and are limited in capacity to, at most, a few IP packets. Optical fiber-based buffers have lower power dissipation but are bulky. The author also concludes that electronic buffering will remain the technology of choice in future high-capacity routers. The power dissipation of high-capacity optical and electronic cross connects for a number of cross connect architectures is compared. The author shows that optical and electronic cross connects dissipate similar power and require a similar chip area. Optical technologies show a potential for inclusion in high-capacity routers, especially as the basis for arrayed-waveguide-grating-based cross connects and as components in E/O/E interconnects. A major challenge in large cross connects, both optical and electronic, will be to efficiently manage the very large number of interconnects between chips and boards. The general conclusion is that electronic technologies are likely to remain as integral components in the signal transmission path of future high-capacity routers. There does not appear to be a compelling case for replacing electronic routers with optically transparent optical packet switches

A Method to Derive SSO Design Rule Considering Jitter Constraint

A method to derive design rules for SSO (Simultaneous Switching Outputs) considering jitter constraint on LSI outputs is proposed. Since conventional design rules do not consider delay change caused by SSO, timing errors have sometimes occurred in output signals especially for a high-speed memory interface which allows very small jitter. A design rule derived by the proposed method includes delay change characteristics of output buffers to consider the jitter constraint. The rule also gives mapping from the jitter constraint to constraint on design parameters such as effective power/ground inductance, number of SSO and drivability of buffers.

Methodology to Improve the Performance of the End-stop Buffers of Suspension Seats

The aim of this study was to optimise the characteristics of the bottom end-stop buffers of compact suspension seats fitted to fork lift trucks with a load-lifting capacity of less than 3.5 tons, earthmoving equipment, farm tractors and plants intended for forestry work. This work required the development of a numerical model of a seat subject to movements likely to cause impact with the end-stop buffer. The model employs a global approach based on modelling the friction phenomenon of the suspension mechanisms by means of Bouc—Wen's behavior law. After validation, the model was used to calculate the optimal characteristics (stiffness, damping and height) of the bottom end-stop buffers of the seat. Prototypes of optimised end-stop buffers were produced from the optimal characteristics calculated. Comparisons between the nominal end-stop buffers and the optimised buffers were made in the laboratory using the excitation signals recorded in the field. The results show that when the optimised end-stop buffers were fixed to the seat instead of the nominal end-stop buffers, between 73% and 93% of the maximum achievable gain was obtained at the acceleration peaks.

Cost‐effective Targeting of Riparian Buffers

This paper develops an integrated economic, hydrologic and GIS modeling framework to examine the cost‐effective targeting of land retirement for establishing riparian buffers in agricultural watersheds. Previous studies have examined the efficiency of targeting large land parcels for retirement or targeting management practices such as conservation tillage but have not considered narrow variable buffer strips. An empirical application of the framework in the Canagagigue Creek watershed in Ontario shows that average and marginal costs of sediment abatement increase at an increasing rate as the environmental goal becomes more stringent. The locations of the buffer strips vary across the watershed and are not necessarily located on those sites with greatest slope or those adjacent to visible streams. Cost effectiveness is further increased if the targeting is extended to allow for the width of the buffer strip to vary by location rather than assume a uniform width. The modeling results have important policy implications for the design of conservation stewardship programs such as setting appropriate environmental health goals based on marginal abatement costs relative to marginal benefits, and setting physical characteristics of the riparian buffers for selection along the drainage network in targeted sub‐catchments.